It is believed that the first European to explore the east coast of Canada was Norse explorer Leif Erikson. In approximately 1000 AD, the Norse built a small short-lived encampment that was occupied sporadically for perhaps 20 years at L'Anse aux Meadows on the northern tip of Newfoundland. No further European exploration occurred until 1497, when Italian seafarer John Cabot explored and claimed Canada's Atlantic coast in the name of King Henry VII of England. In 1534, French explorer Jacques Cartier explored the Gulf of Saint Lawrence where, on July 24, he planted a 10-metre (33 ft) cross bearing the words "Long Live the King of France" and took possession of the territory New France in the name of King Francis I. The early 16th century saw European mariners with navigational techniques pioneered by the Basque and Portuguese establish seasonal whaling and fishing outposts along the Atlantic coast. In general, early settlements during the Age of Discovery appear to have been short-lived due to a combination of the harsh climate, problems with navigating trade routes and competing outputs in Scandinavia.
In 1583, Sir Humphrey Gilbert, by the royal prerogative of Queen Elizabeth I, founded St. John's, Newfoundland, as the first North American English seasonal camp. In 1600, the French established their first seasonal trading post at Tadoussac along the Saint Lawrence. French explorer Samuel de Champlain arrived in 1603 and established the first permanent year-round European settlements at Port Royal (in 1605) and Quebec City (in 1608). Among the colonists of New France, Canadiens extensively settled the Saint Lawrence River valley and Acadians settled the present-day Maritimes, while fur traders and Catholic missionaries explored the Great Lakes, Hudson Bay, and the Mississippi watershed to Louisiana. The Beaver Wars broke out in the mid-17th century over control of the North American fur trade.
The English established additional settlements in Newfoundland in 1610 along with settlements in the Thirteen Colonies to the south. A series of four wars erupted in colonial North America between 1689 and 1763; the later wars of the period constituted the North American theatre of the Seven Years' War. Mainland Nova Scotia came under British rule with the 1713 Treaty of Utrecht, and Canada and most of New France came under British rule in 1763 after the Seven Years' War.


Indigenous peoples in present-day Canada include the First Nations, Inuit, and Métis, the last being of mixed descent who originated in the mid-17th century when First Nations people married European settlers and subsequently developed their own identity.
The first inhabitants of North America are generally hypothesized to have migrated from Siberia by way of the Bering land bridge and arrived at least 14,000 years ago. The Paleo-Indian archeological sites at Old Crow Flats and Bluefish Caves are two of the oldest sites of human habitation in Canada. The characteristics of Indigenous societies included permanent settlements, agriculture, complex societal hierarchies, and trading networks. Some of these cultures had collapsed by the time European explorers arrived in the late 15th and early 16th centuries and have only been discovered through archeological investigations.
The Indigenous population at the time of the first European settlements is estimated to have been between 200,000 and two million, with a figure of 500,000 accepted by Canada's Royal Commission on Aboriginal Peoples. As a consequence of European colonization, the Indigenous population declined by forty to eighty percent, and several First Nations, such as the Beothuk, disappeared. The decline is attributed to several causes, including the transfer of European diseases, such as influenza, measles, and smallpox to which they had no natural immunity, conflicts over the fur trade, conflicts with the colonial authorities and settlers, and the loss of Indigenous lands to settlers and the subsequent collapse of several nations' self-sufficiency.
Although not without conflict, European Canadians' early interactions with First Nations and Inuit populations were relatively peaceful. First Nations and Métis peoples played a critical part in the development of European colonies in Canada, particularly for their role in assisting European coureur des bois and voyageurs in their explorations of the continent during the North American fur trade. The Crown and Indigenous peoples began interactions during the European colonization period, though the Inuit, in general, had more limited interaction with European settlers. From the late 18th century, European Canadians encouraged Indigenous peoples to assimilate into their own culture. These attempts reached a climax in the late 19th and early 20th centuries with forced integration and relocations. A period of redress is underway, which started with the appointment of the Truth and Reconciliation Commission of Canada by the Government of Canada in 2008.


Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over 9.98 million square kilometres (3.85 million square miles), making it the world's second-largest country by total area. Its southern and western border with the United States, stretching 8,891 kilometres (5,525 mi), is the world's longest binational land border. Canada's capital is Ottawa, and its three largest metropolitan areas are Toronto, Montreal, and Vancouver.
Indigenous peoples have continuously inhabited what is now Canada for thousands of years. Beginning in the 16th century, British and French expeditions explored and later settled along the Atlantic coast. As a consequence of various armed conflicts, France ceded nearly all of its colonies in North America in 1763. In 1867, with the union of three British North American colonies through Confederation, Canada was formed as a federal dominion of four provinces. This began an accretion of provinces and territories and a process of increasing autonomy from the United Kingdom. This widening autonomy was highlighted by the Statute of Westminster 1931 and culminated in the Canada Act 1982, which severed the vestiges of legal dependence on the Parliament of the United Kingdom.
Canada is a parliamentary democracy and a constitutional monarchy in the Westminster tradition. The country's head of government is the prime minister—who holds office by virtue of their ability to command the confidence of the elected House of Commons—and is appointed by the governor general, representing the monarch, who serves as head of state. The country is a Commonwealth realm and is officially bilingual (English and French) at the federal level. It ranks among the highest in international measurements of government transparency, civil liberties, quality of life, economic freedom, education, gender equality  and environmental sustainability. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many other countries. Canada's long and complex relationship with the United States has had a significant impact on its economy and culture.
A highly developed country, Canada has the 24th highest nominal per capita income globally and the sixteenth-highest ranking on the Human Development Index. Its advanced economy is the eighth-largest in the world, relying chiefly upon its abundant natural resources and well-developed international trade networks. Canada is part of several major international and intergovernmental institutions or groupings including the United Nations, NATO, the G7, the Group of Ten, the G20, the Organisation for Economic Co-operation and Development (OECD), the World Trade Organization (WTO), the Commonwealth of Nations, the Arctic Council, the Organisation internationale de la Francophonie, the Asia-Pacific Economic Cooperation forum, and the Organization of American States.


The Royal Proclamation of 1763 established First Nation treaty rights, created the Province of Quebec out of New France, and annexed Cape Breton Island to Nova Scotia. St. John's Island (now Prince Edward Island) became a separate colony in 1769. To avert conflict in Quebec, the British Parliament passed the Quebec Act 1774, expanding Quebec's territory to the Great Lakes and Ohio Valley. More importantly, the Quebec Act afforded Quebec special autonomy and rights of self-administration at a time when the Thirteen Colonies were increasingly agitating against British rule. It re-established the French language, Catholic faith, and French civil law there, staving off the growth of an independence movement in contrast to the Thirteen Colonies. The Proclamation and the Quebec Act in turn angered many residents of the Thirteen Colonies, further fuelling anti-British sentiment in the years prior to the American Revolution.
After the successful American War of Independence, the 1783 Treaty of Paris recognized the independence of the newly formed United States and set the terms of peace, ceding British North American territories south of the Great Lakes and east of the Mississippi River to the new country. The American war of independence also caused a large out-migration of Loyalists, the settlers who had fought against American independence. Many moved to Canada, particularly Atlantic Canada, where their arrival changed the demographic distribution of the existing territories. New Brunswick was in turn split from Nova Scotia as part of a reorganization of Loyalist settlements in the Maritimes, which led to the incorporation of Saint John, New Brunswick, as Canada's first city. To accommodate the influx of English-speaking Loyalists in Central Canada, the Constitutional Act of 1791 divided the province of Canada into French-speaking Lower Canada (later Quebec) and English-speaking Upper Canada (later Ontario), granting each its own elected legislative assembly.
The Canadas were the main front in the War of 1812 between the United States and the United Kingdom. Peace came in 1815; no boundaries were changed. Immigration resumed at a higher level, with over 960,000 arrivals from Britain between 1815 and 1850. New arrivals included refugees escaping the Great Irish Famine as well as Gaelic-speaking Scots displaced by the Highland Clearances. Infectious diseases killed between 25 and 33 percent of Europeans who immigrated to Canada before 1891.
The desire for responsible government resulted in the abortive Rebellions of 1837. The Durham Report subsequently recommended responsible government and the assimilation of French Canadians into English culture. The Act of Union 1840 merged the Canadas into a united Province of Canada and responsible government was established for all provinces of British North America east of Lake Superior by 1855. The signing of the Oregon Treaty by Britain and the United States in 1846 ended the Oregon boundary dispute, extending the border westward along the 49th parallel. This paved the way for British colonies on Vancouver Island (1849) and in British Columbia (1858). The Anglo-Russian Treaty of Saint Petersburg (1825) established the border along the Pacific coast, but, even after the US Alaska Purchase of 1867, disputes continued about the exact demarcation of the Alaska–Yukon and Alaska–BC border.


1918 Canadian War bond posters depicting three French women pulling a plow that had been constructed for horses.
French version of the poster roughly translates as "They serve France–Everyone can serve; Buy Victory Bonds".
The same poster in English, with subtle differences in text. "They serve France—How can I serve Canada? Buy Victory Bonds".
Because Britain still maintained control of Canada's foreign affairs under the British North America Act, 1867, its declaration of war in 1914 automatically brought Canada into World War I. Volunteers sent to the Western Front later became part of the Canadian Corps, which played a substantial role in the Battle of Vimy Ridge and other major engagements of the war. Out of approximately 625,000 Canadians who served in World War I, some 60,000 were killed and another 172,000 were wounded. The Conscription Crisis of 1917 erupted when the Unionist Cabinet's proposal to augment the military's dwindling number of active members with conscription was met with vehement objections from French-speaking Quebecers. The Military Service Act brought in compulsory military service, though it, coupled with disputes over French language schools outside Quebec, deeply alienated Francophone Canadians and temporarily split the Liberal Party. In 1919, Canada joined the League of Nations independently of Britain, and the Statute of Westminster, 1931 affirmed Canada's independence.
The Great Depression in Canada during the early 1930s saw an economic downturn, leading to hardship across the country. In response to the downturn, the Co-operative Commonwealth Federation (CCF) in Saskatchewan introduced many elements of a welfare state (as pioneered by Tommy Douglas) in the 1940s and 1950s. On the advice of Prime Minister William Lyon Mackenzie King, war with Germany was declared effective September 10, 1939, by King George VI, seven days after the United Kingdom. The delay underscored Canada's independence.
The first Canadian Army units arrived in Britain in December 1939. In all, over a million Canadians served in the armed forces during World War II and approximately 42,000 were killed and another 55,000 were wounded. Canadian troops played important roles in many key battles of the war, including the failed 1942 Dieppe Raid, the Allied invasion of Italy, the Normandy landings, the Battle of Normandy, and the Battle of the Scheldt in 1944. Canada provided asylum for the Dutch monarchy while that country was occupied and is credited by the Netherlands for major contributions to its liberation from Nazi Germany.
The Canadian economy boomed during the war as its industries manufactured military materiel for Canada, Britain, China, and the Soviet Union. Despite another Conscription Crisis in Quebec in 1944, Canada finished the war with a large army and strong economy.


While a variety of theories have been postulated for the etymological origins of Canada, the name is now accepted as coming from the St. Lawrence Iroquoian word kanata, meaning "village" or "settlement". In 1535, Indigenous inhabitants of the present-day Quebec City region used the word to direct French explorer Jacques Cartier to the village of Stadacona. Cartier later used the word Canada to refer not only to that particular village but to the entire area subject to Donnacona (the chief at Stadacona); by 1545, European books and maps had begun referring to this small region along the Saint Lawrence River as Canada.
From the 16th to the early 18th century, "Canada" referred to the part of New France that lay along the Saint Lawrence River. In 1791, the area became two British colonies called Upper Canada and Lower Canada. These two colonies were collectively named the Canadas until their union as the British Province of Canada in 1841.
Upon Confederation in 1867, Canada was adopted as the legal name for the new country at the London Conference, and the word Dominion was conferred as the country's title. By the 1950s, the term Dominion of Canada was no longer used by the United Kingdom, which considered Canada a "Realm of the Commonwealth". The government of Louis St. Laurent ended the practice of using Dominion in the statutes of Canada in 1951.
The Canada Act 1982, which brought the constitution of Canada fully under Canadian control, referred only to Canada. Later that year, the name of the national holiday was changed from Dominion Day to Canada Day. The term Dominion was used to distinguish the federal government from the provinces, though after the Second World War the term federal had replaced dominion.


The financial crisis of the Great Depression had led the Dominion of Newfoundland to relinquish responsible government in 1934 and become a Crown colony ruled by a British governor. After two referendums, Newfoundlanders voted to join Canada in 1949 as a province.
Canada's post-war economic growth, combined with the policies of successive Liberal governments, led to the emergence of a new Canadian identity, marked by the adoption of the Maple Leaf Flag in 1965, the implementation of official bilingualism (English and French) in 1969, and the institution of official multiculturalism in 1971. Socially democratic programs were also instituted, such as Medicare, the Canada Pension Plan, and Canada Student Loans, though provincial governments, particularly Quebec and Alberta, opposed many of these as incursions into their jurisdictions.
Finally, another series of constitutional conferences resulted in the UK's Canada Act 1982, the patriation of Canada's constitution from the United Kingdom, concurrent with the creation of the Canadian Charter of Rights and Freedoms. Canada had established complete sovereignty as an independent country, although the monarch is retained as sovereign. In 1999, Nunavut became Canada's third territory after a series of negotiations with the federal government.
At the same time, Quebec underwent profound social and economic changes through the Quiet Revolution of the 1960s, giving birth to a secular nationalist movement. The radical Front de libération du Québec (FLQ) ignited the October Crisis with a series of bombings and kidnappings in 1970 and the sovereignist Parti Québécois was elected in 1976, organizing an unsuccessful referendum on sovereignty-association in 1980. Attempts to accommodate Quebec nationalism constitutionally through the Meech Lake Accord failed in 1990. This led to the formation of the Bloc Québécois in Quebec and the invigoration of the Reform Party of Canada in the West. A second referendum followed in 1995, in which sovereignty was rejected by a slimmer margin of 50.6 to 49.4 percent. In 1997, the Supreme Court ruled unilateral secession by a province would be unconstitutional and the Clarity Act was passed by parliament, outlining the terms of a negotiated departure from Confederation.
In addition to the issues of Quebec sovereignty, a number of crises shook Canadian society in the late 1980s and early 1990s. These included the explosion of Air India Flight 182 in 1985, the largest mass murder in Canadian history; the École Polytechnique massacre in 1989, a university shooting targeting female students; and the Oka Crisis of 1990, the first of a number of violent confrontations between the government and Indigenous groups. Canada also joined the Gulf War in 1990 as part of a United States–led coalition force and was active in several peacekeeping missions in the 1990s, including the UNPROFOR mission in the former Yugoslavia. Canada sent troops to Afghanistan in 2001 but declined to join the United States–led invasion of Iraq in 2003.
In 2011, Canadian forces participated in the NATO-led intervention into the Libyan Civil War, and also became involved in battling the Islamic State insurgency in Iraq in the mid-2010s. The COVID-19 pandemic in Canada began on January 27, 2020, with wide social and economic disruption. In 2021, the remains of hundreds of Indigenous people were discovered near the former sites of Canadian Indian residential schools. Administered by the Canadian Catholic Church and funded by the Canadian government from 1828 to 1997, these boarding schools attempted to assimilate Indigenous children into Euro-Canadian culture.


Ontario (/ɒnˈtɛərioʊ/ (listen) on-TAIR-ee-oh; French: [ɔ̃taʁjo]) is one of the thirteen provinces and territories of Canada. Located in Central Canada, it is Canada's most populous province, with 38.3 percent of the country's population, and is the second-largest province by total area (after Quebec). Ontario is Canada's fourth-largest jurisdiction in total area when the territories of the Northwest Territories and Nunavut are included. It is home to the nation's capital city, Ottawa, and the nation's most populous city, Toronto, which is also Ontario's provincial capital.
Ontario is bordered by the province of Manitoba to the west, Hudson Bay and James Bay to the north, and Quebec to the east and northeast, and to the south by the U.S. states of (from west to east) Minnesota, Michigan, Ohio, Pennsylvania, and New York. Almost all of Ontario's 2,700 km (1,678 mi) border with the United States follows inland waterways: from the westerly Lake of the Woods, eastward along the major rivers and lakes of the Great Lakes/Saint Lawrence River drainage system. There is only about 1 km (0.6 mi) of actual land border, made up of portages including Height of Land Portage on the Minnesota border.
The great majority of Ontario's population and arable land is in Southern Ontario. In contrast, Northern Ontario is sparsely populated with cold winters and heavy forestation.


John Graves Simcoe was appointed Upper Canada's first Lieutenant governor in 1793. A second wave of Americans, not all of them necessarily loyalists moved to Upper Canada after 1790 until the pre-war of 1812, many seeking available cheap land, and at the time, lower taxation.
By 1798, there were eight districts: Eastern, Home, Johnstown, London, Midland, Newcastle, Niagara, and Western. By 1826, there were eleven districts: Bathurst, Eastern, Gore, Home, Johnstown, London, Midland, Newcastle, Niagara, Ottawa, and Western. By 1838, there were twenty districts: Bathurst, Brock, Colbourne, Dalhousie, Eastern, Gore, Home, Huron, Johnstown, London, Midland, Newcastle, Niagara, Ottawa, Prince Edward, Simcoe, Talbot, Victoria, Wellington, and Western.
American troops in the War of 1812 invaded Upper Canada across the Niagara River and the Detroit River, but were defeated and pushed back by the British, Canadian fencibles and militias, and First Nations warriors. However, the Americans eventually gained control of Lake Erie and Lake Ontario. The 1813 Battle of York saw American troops defeat the garrison at the Upper Canada capital of York. The Americans looted the town and burned the Upper Canada Parliament Buildings during their brief occupation. The British would burn the American capital of Washington, D.C. in 1814.
After the War of 1812, relative stability allowed for increasing numbers of immigrants to arrive from Europe rather than from the United States. As was the case in the previous decades, this immigration shift was encouraged by the colonial leaders. Despite affordable and often free land, many arriving newcomers, mostly from Britain and Ireland, found frontier life with the harsh climate difficult, and some of those with the means eventually returned home or went south. However, population growth far exceeded emigration in the following decades. It was a mostly agrarian-based society, but canal projects and a new network of plank roads spurred greater trade within the colony and with the United States, thereby improving previously damaged relations over time.
Meanwhile, Ontario's numerous waterways aided travel and transportation into the interior and supplied water power for development. As the population increased, so did the industries and transportation networks, which in turn led to further development. By the end of the century, Ontario vied with Quebec as the nation's leader in terms of growth in population, industry, arts and communications.
Unrest in the colony began to chafe against the aristocratic Family Compact who governed while benefiting economically from the region's resources, and who did not allow elected bodies power. This resentment spurred republican ideals and sowed the seeds for early Canadian nationalism. Accordingly, rebellion in favour of responsible government rose in both regions; Louis-Joseph Papineau led the Lower Canada Rebellion and William Lyon Mackenzie, first Toronto mayor, led the Upper Canada Rebellion. In Upper Canada, the rebellion was quickly a failure. William Lyon Mackenzie escaped to the United States, where he declared the Republic of Canada on Navy Island on the Niagara River.


Paleo-Indians were the first people to settle on the lands of Ontario, arriving there after the Laurentide Ice Sheet melted roughly 11,000 years ago. From them, many ethnocultural groups emerged and came to exist on the lands of Ontario: the Algonquins, Mississaugas, Ojibway, Cree, Odawa, Pottowatomi, and Iroquois.


In the 15th century, the Byzantine Empire fell, prompting Western Europeans to search for new sea routes to the Far East. Around 1522–1523, Giovanni da Verrazzano persuaded King Francis I of France to commission an expedition to find a western route to Cathay (China) via a Northwest Passage. Though this expedition was unsuccessful, it established the name "New France" for northeastern North America. After a few expeditions, France mostly abandoned North America for 50 years because of its financial crisis; France was involved in the Italian Wars and there were religious wars between Protestants and Catholics. Around 1580 however, the rise of the fur trade (particularly the demand for beaver pelts), reignited French interest.

In 1608, Samuel de Champlain established France's first colonial settlement in New France, the Habitation de Québec (now Quebec City), in the colony of Canada (now southern Quebec). Afterwards, French explorers continued to travel west, establishing new villages along the coasts of the Saint Lawrence River. French explorers, the first of which was Étienne Brûlé who explored the Georgian Bay area in 1610–1612, mapped Southern Ontario and called the region the Pays d'en Haut ("Upper Country"), in reference to the region being upstream of the Saint Lawrence River. The colony of the Pays d'en Haut was formally established in 1610 as an administrative dependency of Canada, and was for defence and business rather than a settlement colony. The territory of the Pays-d'en-Haut was quite large and would today include the province of Ontario, as well as, in whole or in part, the American states of Minnesota, Wisconsin, Illinois, Indiana, Michigan, Ohio, Pennsylvania and New York. Indigenous peoples were the vast majority of the Pays d'en Haut population.
 As for Northern Ontario, the English explorer Henry Hudson sailed into Hudson Bay in 1611 and claimed its drainage basin for England. The area would become known as Rupert's Land.
Samuel de Champlain reached Lake Huron in 1615, and French missionaries, such as the Jésuites and Supliciens, began to establish posts along the Great Lakes. The French allied with most Indigenous groups of Ontario, all for the fur trade and for defence against Iroquois attacks (which would later be called the Iroquois Wars). The French would declare their Indigenous allies to be subjects of the King of France and would often act as mediators between different groups. The Iroquois later allied themselves with the British.
From 1634 to 1640, the Huron were devastated by European infectious diseases, such as measles and smallpox, to which they had no immunity. By 1700, the Iroquois had been driven out or left the area that would become Ontario and the Mississaugas of the Ojibwa had settled the north shore of Lake Ontario. The remaining Huron settled north of Quebec.
During the French and Indian War, the North American theater of the Seven Years' War of 1754 to 1763, the British defeated the armies of New France and its Indigenous allies. In the Treaty of Paris 1763 France ceded most of its possessions in North America to Britain. Using the Quebec Act, Britain re-organised the territory into the  Province of Quebec.


Ontario is a term thought to be derived from Indigenous origins, either Ontarí:io, a Huron (Wyandot) word meaning "great lake", or possibly skanadario, which means "beautiful water" or "sparkling water" in the Iroquoian languages. Ontario has about 250,000 freshwater lakes. The first mention of the name Ontario was in 1641, when "Ontario" was used to describe the land on the north shore of the easternmost part of the Great Lakes. It was adopted as the official name of the new province at Confederation in 1867.


Ontario's climate varies by season and location. Three air sources affect it: cold, dry, arctic air from the north (dominant factor during the winter months, and for a longer part of the year in far northern Ontario); Pacific polar air crossing in from the western Canadian Prairies/US Northern Plains; and warm, moist air from the Gulf of Mexico and the Atlantic Ocean. The effects of these major air masses on temperature and precipitation depend mainly on latitude, proximity to major bodies of water and to a small extent, terrain relief. In general, most of Ontario's climate is classified as humid continental.
Ontario has four main climatic regions:
The surrounding Great Lakes greatly influence the climatic region of southern Ontario. During the fall and winter, the release of heat stored by the lakes moderates the climate near the shores. This gives parts of southern Ontario milder winters than mid-continental areas at lower latitudes. Parts of Southwestern Ontario (generally south of a line from Sarnia–Toronto) have a moderate humid continental climate (Köppen climate classification Dfa), similar to the inland Mid-Atlantic states and the Great Lakes portion of the Midwestern United States. The region has warm to hot, humid summers and cold winters. Annual precipitation ranges from 750–1,000 mm (30–39 in) and is well distributed throughout the year. Most of this region lies in the lee of the Great Lakes, making for abundant snow in some areas. In December 2010, the snowbelt set a new record when it was hit by more than a metre of snow within 48 hours.
The next climatic region is Central and Eastern Ontario, which has a moderate humid continental climate (Köppen Dfb). This region has warm and sometimes hot summers with colder, longer winters, ample snowfall (even in regions not directly in the snowbelts) and annual precipitation similar to the rest of Southern Ontario.
The smallest climatic region is located at the most northeastern part of the Niagara Peninsula, which has a temperate humid climate (Köppen Cfa), due to moderating effects by Lake Ontario, the Niagara River and battling air masses from the Gulf of Mexico during the winter months. It is one of the most temperate regions in the entire province.
In the northeastern parts of Ontario, extending south as far as Kirkland Lake, the cold waters of Hudson Bay depress summer temperatures, making it cooler than other locations at similar latitudes. The same is true on the northern shore of Lake Superior, which cools hot, humid air from the south, leading to cooler summer temperatures. Along the eastern shores of Lake Superior and Lake Huron winter temperatures are slightly moderated but come with frequent heavy lake-effect snow squalls that increase seasonal snowfall totals to upwards of 3 m (10 ft) in some places. These regions have higher annual precipitation, in some places over 100 cm (39 in).
The northernmost parts of Ontario – primarily north of 50°N – have a subarctic climate (Köppen Dfc) with long, severely cold winters and short, cool to warm summers with dramatic temperature changes possible in all seasons. With no major mountain ranges blocking sinking Arctic air masses, temperatures of −40 °C (−40 °F) are not uncommon; snow remains on the ground for sometimes over half the year. Snow accumulation can be high in some areas. Precipitation is generally less than 70 cm (28 in) and peaks in the summer months in the form of rain or thunderstorms.
Severe thunderstorms peak in summer. Windsor, in Southern (Southwestern) Ontario, has the most lightning strikes per year in Canada, averaging 33 days of thunderstorm activity per year. In a typical year, Ontario averages 11 confirmed tornado touchdowns. However, over the last 4 years, it has had upwards of 20 tornado touchdowns per year, with the highest frequency in the Windsor-Essex – Chatham Kent area, though few are very destructive (the majority between F0 to F2 on the Fujita scale). Ontario had a record 29 tornadoes in both 2006 and 2009. Tropical depression remnants occasionally bring heavy rains and winds in the south, but are rarely deadly. A notable exception was Hurricane Hazel which struck Southern Ontario centred on Toronto, in October 1954.


In 1782–1784, 5,000 United Empire Loyalists entered what is now Ontario following the American Revolution. The Kingdom of Great Britain granted them 200 acres (81 ha) land and other items with which to rebuild their lives. The British also set up reserves in Ontario for the Mohawks who had fought for the British and had lost their land in New York state. Other Iroquois, also displaced from New York were resettled in 1784 at the Six Nations reserve at the west end of Lake Ontario. The Mississaugas, displaced by European settlements, would later move to Six Nations also.
After the American War of Independence, the first reserves for First Nations were established. These are situated at Six Nations (1784), Tyendinaga (1793) and Akwesasne (1795). Six Nations and Tyendinaga were established by the British for those Indigenous groups who had fought on the side of the British, and were expelled from the new United States. Akwesasne was a pre-existing Mohawk community and its borders were formalized under the 1795 Jay Treaty.
In 1788, while part of the Province of Quebec, southern Ontario was divided into four districts: Hesse, Lunenburg, Mecklenburg, and Nassau. In 1792, the four districts were renamed: Hesse became the Western District, Lunenburg became the Eastern District, Mecklenburg became the Midland District, and Nassau became the Home District. Counties were created within the districts.
The population of Canada west of the St. Lawrence-Ottawa River confluence substantially increased during this period, a fact recognized by the Constitutional Act of 1791, which split Quebec into the Canadas: Upper Canada southwest of the St. Lawrence-Ottawa River confluence, and Lower Canada east of it.


The thinly populated Canadian Shield in the northwestern and central portions, which comprises over half the land area of Ontario. Although this area mostly does not support agriculture, it is rich in minerals, partly covered by the Central and Midwestern Canadian Shield forests, and studded with lakes and rivers. Northern Ontario is subdivided into two sub-regions: Northwestern Ontario and Northeastern Ontario.
The virtually unpopulated Hudson Bay Lowlands in the extreme north and northeast, mainly swampy and sparsely forested.
Southern Ontario, which is further sub-divided into four sub-regions: Central Ontario (although not actually the province's geographic centre), Eastern Ontario, Golden Horseshoe and Southwestern Ontario (parts of which were formerly referred to as Western Ontario).
Despite the absence of any mountainous terrain in the province, there are large areas of uplands, particularly within the Canadian Shield which traverses the province from northwest to southeast and also above the Niagara Escarpment which crosses the south. The highest point is Ishpatina Ridge at 693 metres (2,274 ft) above sea level in Temagami, Northeastern Ontario. In the south, elevations of over 500 m (1,640 ft) are surpassed near Collingwood, above the Blue Mountains in the Dundalk Highlands and in hilltops near the Madawaska River in Renfrew County.
The Carolinian forest zone covers most of the southwestern region of the province. The temperate and fertile Great Lakes-Saint Lawrence Valley in the south is part of the Eastern Great Lakes lowland forests ecoregion where the forest has now been largely replaced by agriculture, industrial and urban development. A well-known geographic feature is Niagara Falls, part of the Niagara Escarpment. The Saint Lawrence Seaway allows navigation to and from the Atlantic Ocean as far inland as Thunder Bay in Northwestern Ontario. Northern Ontario covers approximately 87% of the province's surface area; conversely Southern Ontario contains 94% of the population.
Point Pelee is a peninsula of Lake Erie in southwestern Ontario (near Windsor and Detroit, Michigan) that is the southernmost extent of Canada's mainland. Pelee Island and Middle Island in Lake Erie extend slightly farther. All are south of 42°N – slightly farther south than the northern border of California.


Building upon the gene-chromosome theory of heredity that originated with Gregor Mendel (1822–1884), August Weismann (1834–1914) proved that inheritance only takes place through gametes. No other cells can pass on inherited characters. The work of Katherine Esau (1898–1997) on plant anatomy is still a major foundation of modern botany. Her books Plant Anatomy and Anatomy of Seed Plants have been key plant structural biology texts for more than half a century.
The discipline of plant ecology was pioneered in the late 19th century by botanists such as Eugenius Warming, who produced the hypothesis that plants form communities, and his mentor and successor Christen C. Raunkiær whose system for describing plant life forms is still in use today. The concept that the composition of plant communities such as temperate broadleaf forest changes by a process of ecological succession was developed by Henry Chandler Cowles, Arthur Tansley and Frederic Clements. Clements is credited with the idea of climax vegetation as the most complex vegetation that an environment can support and Tansley introduced the concept of ecosystems to biology. Building on the extensive earlier work of Alphonse de Candolle, Nikolai Vavilov (1887–1943) produced accounts of the biogeography, centres of origin, and evolutionary history of economic plants.
Particularly since the mid-1960s there have been advances in understanding of the physics of plant physiological processes such as transpiration (the transport of water within plant tissues),  the temperature dependence of rates of water evaporation from the leaf surface and the molecular diffusion of water vapour and carbon dioxide through stomatal apertures. These developments, coupled with new methods for measuring the size of stomatal apertures, and the rate of photosynthesis have enabled precise description of the rates of gas exchange between plants and the atmosphere. Innovations in statistical analysis by Ronald Fisher, Frank Yates and others at Rothamsted Experimental Station facilitated rational experimental design and data analysis in botanical research. The discovery and identification of the auxin plant hormones by Kenneth V. Thimann in 1948 enabled regulation of plant growth by externally applied chemicals. Frederick Campion Steward pioneered techniques of micropropagation and plant tissue culture controlled by plant hormones. The synthetic auxin 2,4-Dichlorophenoxyacetic acid or 2,4-D was one of the first commercial synthetic herbicides.
20th century developments in plant biochemistry have been driven by modern techniques of organic chemical analysis, such as spectroscopy, chromatography and electrophoresis. With the rise of the related molecular-scale biological approaches of molecular biology, genomics, proteomics and metabolomics, the relationship between the plant genome and most aspects of the biochemistry, physiology, morphology and behaviour of plants can be subjected to detailed experimental analysis. The concept originally stated by Gottlieb Haberlandt in 1902 that all plant cells are totipotent and can be grown in vitro ultimately enabled the use of genetic engineering experimentally to knock out a gene or genes responsible for a specific trait, or to add genes such as GFP that report when a gene of interest is being expressed. These technologies enable the biotechnological use of whole plants or plant cell cultures grown in bioreactors to synthesise pesticides, antibiotics or other pharmaceuticals, as well as the practical application of genetically modified crops designed for traits such as improved yield.
Modern morphology recognises a continuum between the major morphological categories of root, stem (caulome), leaf (phyllome) and trichome. Furthermore, it emphasises structural dynamics. Modern systematics aims to reflect and discover phylogenetic relationships between plants. Modern Molecular phylogenetics largely ignores morphological characters, relying on DNA sequences as data. Molecular analysis of DNA sequences from most families of flowering plants enabled the Angiosperm Phylogeny Group to publish in 1998 a phylogeny of flowering plants, answering many of the questions about relationships among angiosperm families and species. The theoretical possibility of a practical method for identification of plant species and commercial varieties by DNA barcoding is the subject of active current research.


Botany originated as herbalism, the study and use of plants for their medicinal properties. The early recorded history of botany includes many ancient writings and plant classifications. Examples of early botanical works have been found in ancient texts from India dating back to before 1100 BCE, Ancient Egypt, in archaic Avestan writings, and in works from China purportedly from before 221 BCE.
Modern botany traces its roots back to Ancient Greece specifically to Theophrastus (c. 371–287 BCE), a student of Aristotle who invented and described many of its principles and is widely regarded in the scientific community as the "Father of Botany". His major works, Enquiry into Plants and On the Causes of Plants, constitute the most important contributions to botanical science until the Middle Ages, almost seventeen centuries later.
Another work from Ancient Greece that made an early impact on botany is De Materia Medica, a five-volume encyclopedia about herbal medicine written in the middle of the first century by Greek physician and pharmacologist Pedanius Dioscorides. De Materia Medica was widely read for more than 1,500 years. Important contributions from the medieval Muslim world include Ibn Wahshiyya's Nabatean Agriculture, Abū Ḥanīfa Dīnawarī's (828–896) the Book of Plants, and Ibn Bassal's The Classification of Soils. In the early 13th century, Abu al-Abbas al-Nabati, and Ibn al-Baitar (d. 1248) wrote on botany in a systematic and scientific manner.
In the mid-16th century, botanical gardens were founded in a number of Italian universities. The Padua botanical garden in 1545 is usually considered to be the first which is still in its original location. These gardens continued the practical value of earlier "physic gardens", often associated with monasteries, in which plants were cultivated for medical use. They supported the growth of botany as an academic subject. Lectures were given about the plants grown in the gardens and their medical uses demonstrated. Botanical gardens came much later to northern Europe; the first in England was the University of Oxford Botanic Garden in 1621. Throughout this period, botany remained firmly subordinate to medicine.
German physician Leonhart Fuchs (1501–1566) was one of "the three German fathers of botany", along with theologian Otto Brunfels (1489–1534) and physician Hieronymus Bock (1498–1554) (also called Hieronymus Tragus). Fuchs and Brunfels broke away from the tradition of copying earlier works to make original observations of their own. Bock created his own system of plant classification.
Physician Valerius Cordus (1515–1544) authored a botanically and pharmacologically important herbal Historia Plantarum in 1544 and a pharmacopoeia of lasting importance, the Dispensatorium in 1546. Naturalist Conrad von Gesner (1516–1565) and herbalist John Gerard (1545–c. 1611) published herbals covering the medicinal uses of plants. Naturalist Ulisse Aldrovandi (1522–1605) was considered the father of natural history, which included the study of plants. In 1665, using an early microscope, Polymath Robert Hooke discovered cells, a term he coined, in cork, and a short time later in living plant tissue.


In botany and horticulture, deciduous plants, including trees, shrubs and herbaceous perennials, are those that lose all of their leaves for part of the year. This process is called abscission. In some cases leaf loss coincides with winter—namely in temperate or polar climates. In other parts of the world, including tropical, subtropical, and arid regions, plants lose their leaves during the dry season or other seasons, depending on variations in rainfall.
The converse of deciduous is evergreen, where foliage is shed on a different schedule from deciduous plants, therefore appearing to remain green year round because not all the leaves are shed at the same time. Plants that are intermediate may be called semi-deciduous; they lose old foliage as new growth begins. Other plants are semi-evergreen and lose their leaves before the next growing season, retaining some during winter or dry periods.
Many deciduous plants flower during the period when they are leafless, as this increases the effectiveness of pollination. The absence of leaves improves wind transmission of pollen for wind-pollinated plants and increases the visibility of the flowers to insects in insect-pollinated plants. This strategy is not without risks, as the flowers can be damaged by frost or, in dry season regions, result in water stress on the plant.
The conditions that trigger leaf out or leaf flushing in spring can vary depending on the species or genera of plant. Most herbaceous perennials and some woody plants are triggered to leaf out by warming air or soil temperatures, for example birches (Betula) and willows (Salix) will attempt to send out flowers or leaves if there are a few days where ambient air temperatures exceed 10 °C (50 °F). This strategy is risky as a renewed burst of cold air may freeze off the new growth. Other woody plants such as oaks, walnuts, and hickories leaf out based on photoperiod, meaning they wait until the day length is long enough. These tend to be plants that have frost-intolerant foliage, so leaf out is held off until late spring when the danger of frost has largely passed.
Leaf drop in the fall months is based on photoperiod and varies by genera and species. Walnuts tend to drop their leaves early while some trees such as Norway Maple and willows have extremely late leaf drop, often in the middle of November.
Leaf drop or abscission involves complex physiological signals and changes within plants. The process of photosynthesis steadily degrades the supply of chlorophylls in foliage; plants normally replenish chlorophylls during the summer months. When autumn arrives and the days are shorter or when plants are drought-stressed, deciduous trees decrease chlorophyll pigment production, allowing other pigments present in the leaf to become apparent, resulting in non-green colored foliage. The brightest leaf colors are produced when days grow short and nights are cool, but remain above freezing. These other pigments include carotenoids that are yellow, brown, and orange. Anthocyanin pigments produce red and purple colors, though they are not always present in the leaves. Rather, they are produced in the foliage in late summer, when sugars are trapped in the leaves after the process of abscission begins. Parts of the world that have showy displays of bright autumn colors are limited to locations where days become short and nights are cool. In other parts of the world, the leaves of deciduous trees simply fall off without turning the bright colors produced from the accumulation of anthocyanin pigments. (See also: Autumn leaf color)
The beginnings of leaf drop starts when an abscission layer is formed between the leaf petiole and the stem. This layer is formed in the spring during active new growth of the leaf; it consists of layers of cells that can separate from each other. The cells are sensitive to a plant hormone called auxin that is produced by the leaf and other parts of the plant. When auxin coming from the leaf is produced at a rate consistent with that from the body of the plant, the cells of the abscission layer remain connected; in autumn, or when under stress, the auxin flow from the leaf decreases or stops, triggering cellular elongation within the abscission layer. The elongation of these cells break the connection between the different cell layers, allowing the leaf to break away from the plant. It also forms a layer that seals the break, so the plant does not lose sap.
Some trees, particularly oaks and beeches, exhibit a behavior known as "marcescence" whereby dead leaves are not shed in the fall and remain on the tree until being blown off by the weather. This is caused by incomplete development of the abscission layer. It is mainly seen in the seedling and sapling stage, although mature trees may have marcescence of leaves on the lower branches.
A number of deciduous plants remove nitrogen and carbon from the foliage before they are shed and store them in the form of proteins in the vacuoles of parenchyma cells in the roots and the inner bark. In the spring, these proteins are used as a nitrogen source during the growth of new leaves or flowers.


Plants with deciduous foliage have advantages and disadvantages compared to plants with evergreen foliage.

Since deciduous plants lose their leaves to conserve water or to better survive winter weather conditions, they must regrow new foliage during the next suitable growing season; this uses resources which evergreens do not need to expend.

Evergreens suffer greater water loss during the winter and they also can experience greater predation pressure, especially when small. Deciduous trees experience much less branch and trunk breakage from glaze ice storms when leafless, and plants can reduce water loss due to the reduction in availability of liquid water during cold winter days.
Losing leaves in winter may reduce damage from insects; repairing leaves and keeping them functional may be more costly than just losing and regrowing them. Removing leaves also reduces cavitation which can damage xylem vessels in plants. This then allows deciduous plants to have xylem vessels with larger diameters and therefore a greater rate of transpiration (and hence CO₂ uptake as this occurs when stomata are open) during the summer growth period.


Forests where a majority of the trees lose their foliage at the end of the typical growing season are called deciduous forests. These forests are found in many areas worldwide and have distinctive ecosystems, understory growth, and soil dynamics.
Two distinctive types of deciduous forest are found growing around the world.
Temperate deciduous forest biomes are plant communities distributed in North and South America, Asia, Southern slopes of the Himalayas, Europe and for cultivation purposes in Oceania. They have formed under climatic conditions which have great seasonable temperature variability with growth occurring during warm summers and leaf drop in autumn and dormancy during cold winters. These seasonally distinctive communities have diverse life forms that are impacted greatly by the seasonality of their climate, mainly temperature and precipitation rates. These varying and regionally different ecological conditions produce distinctive forest plant communities in different regions.
Tropical and subtropical deciduous forest biomes have developed in response not to seasonal temperature variations but to seasonal rainfall patterns. During prolonged dry periods the foliage is dropped to conserve water and prevent death from drought. Leaf drop is not seasonally dependent as it is in temperate climates, and can occur any time of year and varies by region of the world. Even within a small local area there can be variations in the timing and duration of leaf drop; different sides of the same mountain and areas that have high water tables or areas along streams and rivers can produce a patchwork of leafy and leafless trees.


The deciduous characteristic has developed repeatedly among woody plants. Trees include maple, many oaks and nothofagus, elm, beech, aspen, and birch, among others, as well as a number of coniferous genera, such as larch and Metasequoia. Deciduous shrubs include honeysuckle, viburnum, and many others. Most temperate woody vines are also deciduous, including grapes, poison ivy, Virginia creeper, wisteria, etc. The characteristic is useful in plant identification; for instance in parts of Southern California and the American Southeast, deciduous and evergreen oak species may grow side by side.
Periods of leaf fall often coincide with seasons: winter in the case of cool-climate plants or the dry-season in the case of tropical plants, however there are no deciduous species among tree-like monocotyledonous plants, e.g. palms, yuccas, and dracaenas. The hydrangea hirta is a deciduous woody shrub found in Japan.


Measurement of pH below about 2.5 (ca. 0.003 mol/dm³ acid) and above about 10.5 (ca. 0.0003 mol/dm³ alkaline) requires special procedures because, when using the glass electrode, the Nernst law breaks down under those conditions. Various factors contribute to this. It cannot be assumed that liquid junction potentials are independent of pH. Also, extreme pH implies that the solution is concentrated, so electrode potentials are affected by ionic strength variation. At high pH the glass electrode may be affected by "alkaline error", because the electrode becomes sensitive to the concentration of cations such as Na⁺ and K⁺ in the solution. Specially constructed electrodes are available which partly overcome these problems.
Runoff from mines or mine tailings can produce some very low pH values.


Indicators may be used to measure pH, by making use of the fact that their color changes with pH. Visual comparison of the color of a test solution with a standard color chart provides a means to measure pH accurate to the nearest whole number. More precise measurements are possible if the color is measured spectrophotometrically, using a colorimeter or spectrophotometer.
Universal indicator consists of a mixture of indicators such that there is a continuous color change from about pH 2 to pH 10. Universal indicator paper is made from absorbent paper that has been impregnated with universal indicator. Another method of measuring pH is using an electronic pH meter.


The concept of pH was first introduced by the Danish chemist Søren Peder Lauritz Sørensen at the Carlsberg Laboratory in 1909 and was revised to the modern pH in 1924 to accommodate definitions and measurements in terms of electrochemical cells. In the first papers, the notation had H• as a subscript to the lowercase p, thus: pH•.
For the sign p, I propose the name 'hydrogen ion exponent' and the symbol pH•. Then, for the hydrogen ion exponent (pH•) of a solution, the negative value of the Briggsian logarithm of the related hydrogen ion normality factor is to be understood.
The exact meaning of the letter p in "pH" is disputed, as Sørensen did not explain why he used it. Sørensen describes a way of measuring pH using potential differences, and it represents the negative power of 10 in the concentration of hydrogen ions. The letter p could stand for the French puissance, German Potenz, or Danish potens, meaning "power", or it could mean "potential". All the words for these start with the letter p in French, German, and Danish—all languages Sørensen published in: Carlsberg Laboratory was French-speaking, German was the dominant language of scientific publishing, and Sørensen was Danish. He also used the letter q in much the same way elsewhere in the paper. He might also just have labelled the test solution "p" and the reference solution "q" arbitrarily; these letters are often paired. Some literature sources state that the "pH" stands for the Latin term pondus hydrogenii (quantity of hydrogen) or potentia hydrogenii (power of hydrogen), although this is not supported by Sørensen's writings.
Currently in chemistry, the p stands for "decimal logarithm of", and is also used in the term pKₐ, used for acid dissociation constants and pOH, the equivalent for hydroxide ions.
Bacteriologist Alice C. Evans, famed for her work's influence on dairying and food safety, credited William Mansfield Clark and colleagues (of whom she was one) with developing pH measuring methods in the 1910s, which had a wide influence on laboratory and industrial use thereafter. In her memoir, she does not mention how much, or how little, Clark and colleagues knew about Sørensen's work a few years prior. She said:
In these studies [of bacterial metabolism] Dr. Clark's attention was directed to the effect of acid on the growth of bacteria. He found that it is the intensity of the acid in terms of hydrogen-ion concentration that affects their growth. But existing methods of measuring acidity determined the quantity, not the intensity, of the acid. Next, with his collaborators, Dr. Clark developed accurate methods for measuring hydrogen-ion concentration. These methods replaced the inaccurate titration method of determining the acid content in use in biologic laboratories throughout the world. Also they were found to be applicable in many industrial and other processes in which they came into wide usage.
The first electronic method for measuring pH was invented by Arnold Orville Beckman, a professor at California Institute of Technology in 1934. It was in response to local citrus grower Sunkist that wanted a better method for quickly testing the pH of lemons they were picking from their nearby orchards.


pOH is sometimes used as a measure of the concentration of hydroxide ions, OH⁻. pOH values are derived from pH measurements. The concentration of hydroxide ions in water is related to the concentration of hydrogen ions by
{\displaystyle [{\ce {OH^-}}]={\frac {K_{{\ce {W}}}}{[{\ce {H^+}}]}}}
where KW is the self-ionization constant of water. Taking logarithms
{\displaystyle {\ce {pOH}}={\ce {p}}K_{{\ce {W}}}-{\ce {pH}}}
So, at room temperature, pOH ≈ 14 − pH. However this relationship is not strictly valid in other circumstances, such as in measurements of soil alkalinity.


Which plants are chosen to be named as cultivars is simply a matter of convenience as the category was created to serve the practical needs of horticulture, agriculture, and forestry.
Members of a particular cultivar are not necessarily genetically identical. The Cultivated Plant Code emphasizes that different cultivated plants may be accepted as different cultivars, even if they have the same genome, while cultivated plants with different genomes may be regarded as the same cultivar. The production of cultivars generally entails considerable human involvement although in a few cases it may be as little as simply selecting variation from plants growing in the wild (whether by collecting growing tissue to propagate from or by gathering seed).
Cultivars generally occur as ornamentals and food crops: Malus 'Granny Smith' and Malus 'Red Delicious' are cultivars of apples propagated by cuttings or grafting, Lactuca 'Red Sails' and Lactuca 'Great Lakes' are lettuce cultivars propagated by seeds. Named cultivars of Hosta and Hemerocallis plants are cultivars produced by micropropagation or division.


Genetically modified plants with characteristics resulting from the deliberate implantation of genetic material from a different germplasm may form a cultivar. However, the International Code of Nomenclature for Cultivated Plants notes, "In practice such an assemblage is often marketed from one or more lines or multilines that have been genetically modified. These lines or multilines often remain in a constant state of development which makes the naming of such an assemblage as a cultivar a futile exercise."  However, retired transgenic varieties such as the fish tomato, which are no longer being developed, do not run into this obstacle and can be given a cultivar name.
Cultivars may be selected because of a change in the ploidy level of a plant which may produce more desirable characteristics.


Hardwoods are employed in a large range of applications, including fuel, tools, construction, boat building, furniture making, musical instruments, flooring, cooking, barrels, and manufacture of charcoal. Solid hardwood joinery tends to be expensive compared to softwood. In the past, tropical hardwoods were easily available, but the supply of some species, such as Burma teak and mahogany, is now becoming scarce due to over-exploitation. Cheaper "hardwood" doors, for instance, now consist of a thin veneer bonded to a core of softwood, plywood or medium-density fibreboard (MDF). Hardwoods may be used in a variety of objects, but are most frequently seen in furniture or musical instruments because of their density which adds to durability, appearance, and performance. Different species of hardwood lend themselves to different end uses or construction processes. This is due to the variety of characteristics apparent in different timbers, including density, grain, pore size, growth and fibre pattern, flexibility and ability to be steam bent. For example, the interlocked grain of elm wood (Ulmus spp.) makes it suitable for the making of chair seats where the driving in of legs and other components can cause splitting in other woods.


Hardwoods are produced by angiosperm trees that reproduce by flowers, and have broad leaves. Many species are deciduous. Those of temperate regions lose their leaves every autumn as temperatures fall and are dormant in the winter, but those of tropical regions may shed their leaves in response to seasonal or sporadic periods of drought.  Hardwood from deciduous species, such as oak, normally shows annual growth rings, but these may be absent in some tropical hardwoods.
Hardwoods have a more complex structure than softwoods and are often much slower growing as a result. The dominant feature separating "hardwoods" from softwoods is the presence of pores, or vessels. The vessels may show considerable variation in size, shape of perforation plates (simple, scalariform, reticulate, foraminate), and structure of cell wall, such as spiral thickenings.
As the name suggests, the wood from these trees is generally harder than that of softwoods, but there are significant exceptions.  In both groups there is an enormous variation in actual wood hardness, with the range in density in hardwoods completely including that of softwoods; some hardwoods (e.g., balsa) are softer than most softwoods, while yew is an example of a hard softwood.


There is a correlation between density and calories/volume. This makes the denser hardwoods like oak, cherry, and apple more suited for camp fires, cooking fires, and smoking meat, as they tend to burn hotter and longer than softwoods like pine or cedar whose low-density construction and highly-flammable pitch make them burn quickly and without producing quite as much heat.


The structural polymers of hardwoods are cellulose, hemicellulose, and lignin. The constituents of hardwood lignin differs from those included in softwood. Sinapyl alcohol and coniferyl alcohol are the main monomers of hardwood lignin.
Hardwoods contain less amount of non-structural constituents, named extractives, than softwoods. These extractives are usually categorized into three broad groups: aliphatic compounds, terpenes and phenolic compounds. Aliphatic compounds found in hardwoods include fatty acids, fatty alcohols and their esters with glycerol, fatty alcohols (waxes) and sterols (steryl esters), hydrocarbons, such as alkanes, sterols, such as sitosterol, sitostanol and campesterol. The terpene content of the hardwood significantly differs from the softwood, and mainly consistis of triterpenoids, polyprenols and other higher terpenes. Triterpenoids commonly purified from hardwoods include cycloartenol, betulin and squalene. Hardwood polyterpenes are rubber, gutta percha, gutta-balatá and betulaprenols. Although in small quantities, hardwoods also contain mono-, sesqui- and diterpenes, such as α- and β-pinenes, 3-carene, β-myrcene, limonene, hinokitiol, δ-cadinene, α- and δ-cadinols, borneol. Hardwood is rich in phenolic compounds, such as stilbenes, lignans, norlignans, tannins, flavonoids.


The primary material needed for the process of humification are plant materials. The composition of humus varies dependent on the composition of the primary materials and the secondary microbial and animal products. The decomposition rate of the different compounds will affect the composition of the humus.
It is difficult to define humus precisely because it is a very complex substance which is not fully understood. Humus is different from decomposing soil organic matter. The latter looks rough and has visible remains of the original plant or animal matter. Fully humified humus, on the contrary, has a uniformly dark, spongy, and jelly-like appearance, and is amorphous; it may gradually decay over several years or persist for millennia. It has no determinate shape, structure, or quality. However, when examined under a microscope, humus may reveal tiny plant, animal, or microbial remains that have been mechanically, but not chemically, degraded. This suggests an ambiguous boundary between humus and soil organic matter. While distinct, humus is an integral part of soil organic matter.
There is little data available on the composition of forest humus because it is a complex mixture that is challenging for researchers to analyze. Researchers in the 1940s and 1960s tried using chemical separation to analyze plant and humic compounds in forest soil, but this proved impossible. Further research has been done in more recent years, though it remains an active field of study.


Aegletes (/əˈɡliːtiːz/ ə-GLEE-teez; Αἰγλήτης, Aiglētēs), from αἴγλη, "light of the sun"
Helius (/ˈhiːliəs/ HEE-lee-əs; Ἥλιος, Helios), literally "sun"
Lyceus (/laɪˈsiːəs/ ly-SEE-əs; Λύκειος, Lykeios, from Proto-Greek *λύκη), "light". The meaning of the epithet "Lyceus" later became associated with Apollo's mother Leto, who was the patron goddess of Lycia (Λυκία) and who was identified with the wolf (λύκος).
Phanaeus (/fəˈniːəs/ fə-NEE-əs; Φαναῖος, Phanaios), literally "giving or bringing light"
Phoebus (/ˈfiːbəs/ FEE-bəs; Φοῖβος, Phoibos), literally "bright", his most commonly used epithet by both the Greeks and Romans
Sol (Roman) (/sɒl/), "sun" in Latin


Apollo's birthplace was Mount Cynthus on the island of Delos.
Cynthius (/ˈsɪnθiəs/ SIN-thee-əs; Κύνθιος, Kunthios), literally "Cynthian"
Cynthogenes (/sɪnˈθɒdʒɪniːz/ sin-THOJ-in-eez; Κυνθογενής, Kynthogenēs), literally "born of Cynthus"
Delius (/ˈdiːliəs/ DEE-lee-əs; Δήλιος, Delios), literally "Delian"
Didymaeus (/ˌdɪdɪˈmiːəs/ DID-im-EE-əs; Διδυμαῖος, Didymaios) from δίδυμος, "twin", as the twin of Artemis


January 2 – Erroll Garner, American musician (b. 1921)
January 4 – Ibrahim Biçakçiu, Albanian politician, 2-time Prime Minister of Albania leader of World War II (b. 1905)
January 5 – Artur Adson, Estonian poet, writer and theatre critic (b. 1889)
January 14
Anthony Eden, British politician, 62nd Prime Minister of the United Kingdom (b. 1897)
Peter Finch, English-born actor (b. 1916)
Anaïs Nin, French diarist and writer (b. 1903)
January 17 – Gary Gilmore, American murderer (b. 1940)
January 18
Džemal Bijedić, Yugoslavian politician, 27th Prime Minister of Yugoslavia (b. 1917)
Carl Zuckmayer, German writer and playwright  (b. 1896)
January 19 – Yvonne Printemps, French singer and actress (b. 1895)
January 20 – Dimitrios Kiousopoulos, Prime Minister of Greece (b. 1892)
January 23 – Pascual Pérez, Argentine world Flyweight boxing champion (b. 1926)
January 26 – Dietrich von Hildebrand, German philosopher and theologian (b. 1889)
January 29 – Freddie Prinze, American actor and comedian (b. 1954)


May 5 – Ludwig Erhard, German politician, 28th Chancellor of Germany (West Germany) (b. 1897)
May 7 – Prince Xavier of Bourbon-Parma, Spanish Carlist pretender (b. 1889)
May 9 – James Jones, American writer (b. 1921)
May 10 – Joan Crawford, American actress (b. c. 1904)
May 13 – Otto Deßloch, German World War II Luftwaffe general (b. 1889)
May 15 – Herbert Wilcox, British film director and producer (b. 1892)
May 16 – Modibo Keïta, 1st President of Mali (b. 1915)
May 25 – Willoughby Norrie, British army general and Governor-General of New Zealand (b. 1893)
May 31 – William Castle, American film director (b. 1914)


March 1 – Diallo Telli, Guinean diplomat and politician, 1st Secretary General of the Organisation of African Unity (b. 1925)
March 3
Brian Faulkner, last Prime Minister of Northern Ireland (b. 1921)
Percy Marmont, American stage and screen actor (b. 1883)
March 4
Andrés Caicedo, Colombian writer (b. 1951)
Lutz Graf Schwerin von Krosigk, German jurist and senior government official, last führer of Nazi Germany (b. 1887)
March 5 – Tom Pryce, British Formula One racing driver (b. 1949)
March 8 – Henry Hull, American actor (b. 1890)
March 10
E. Power Biggs, English-American organist (b. 1906)
Willem Schermerhorn, Dutch politician and civil engineer, 28th Prime Minister of the Netherlands (b. 1894)
March 14 – Fannie Lou Hamer, American civil rights activist (b. 1917)
March 15 – Antonino Rocca, Italian professional wrestler (b. 1921)
March 17 – Claude Roger-Marx, French writer, and playwright (b. 1888)
March 18 – Marien Ngouabi, 3rd President of Congo (b. 1938)
March 19 – William L. Laurence, Jewish Lithuanian-American journalist (b. 1888)
March 20 – Charles Lyttelton, 10th Viscount Cobham, English politician, 9th Governor-General of New Zealand (b. 1909)
March 29 – Eugen Wüster, industrialist and terminologist (b. 1898)
March 30 – Abdel Halim Hafez, Egyptian singer and actor (b. 1929)


1977
January
February
March
April
May
June
July
August
September
October
November
December
1977 (MCMLXXVII) was a common year starting on Saturday of the Gregorian calendar, the 1977th year of the Common Era (CE) and Anno Domini (AD) designations, the 977th  year of the 2nd millennium, the 77th  year of the 20th century, and the  8th   year of the 1970s decade.


April 2 – John Whitaker, British gymnast (b. 1886)
April 5 – Carlos Prío Socarrás, 11th President of Cuba (b. 1903)
April 7 – Karl Ritter, German film producer and director (b. 1888)
April 11 – Jacques Prévert, French poet and screenwriter (b. 1900)
April 17 – William Conway, Northern Irish cardinal (b. 1913)
April 20
Wilmer Allison, American tennis champion (b. 1904)
Bryan Foy, American film producer and director (b. 1896)
April 21 – Gummo Marx, American actor and comedian (b. 1892)
April 27
Stanley Adams, American actor (b. 1915)
Charles Alston, American artist and sculptor (b. 1907)
April 28
Ricardo Cortez, American actor (b. 1899)
Sepp Herberger, German footballer and manager (b. 1897)


April 1 – Hard Times begins serialisation in Charles Dickens' magazine, Household Words.
April 16 – The United States packet ship Powhattan is wrecked off the New Jersey shore, with more than 200 victims.
May 18 – The Catholic University of Ireland (forerunner of University College Dublin) is founded.
May 27 – Taiping Rebellion: United States diplomatic minister Robert McLane arrives at the Heavenly Capital aboard the American warship USS Susquehanna.
May 30 – The Kansas–Nebraska Act becomes law (replacing the Missouri Compromise of 1820), creating the Kansas Territory and the Nebraska Territory, west of the State of Missouri and the State of Iowa. The Kansas–Nebraska Act also establishes that these two new Territories will decide either to allow or disallow slavery, depending on balloting by their residents (these areas would have been strictly "free territory" under the Missouri Compromise, which allowed slavery in the State of Missouri but disallowed it in any other new state north of latitude 36° 30', which forms most of the southern boundary of Missouri. This prohibition of slavery extended all the way from the western boundary of Missouri to the Pacific Ocean).
June – The Grand Excursion takes prominent Eastern United States inhabitants from Chicago to Rock Island, Illinois by railroad, then up the Mississippi River to Saint Paul, Minnesota by steamboat.
June 10 – The first class of the United States Naval Academy graduates at Annapolis, Maryland.
June 21 – Battle of Bomarsund in Åland off the coast of Finland: British Royal Navy seaman's mate Charles Davis Lucas throws a live Russian artillery shell overboard by hand before it explodes, for which he is awarded the first Victoria Cross in 1857.


January 8 – William Beresford, 1st Viscount Beresford, British general and politician (b. 1768)
February 17 – John Martin, English painter (b. 1789)
February 25 – Ann Walker, English landowner and philanthropist (b. 1803)
March 6 – Charles Vane, 3rd Marquess of Londonderry (b. 1778)
March 11 – Willard Richards, American religious leader (b. 1804)
March 13
Sir Thomas Talfourd, English jurist (b. 1795)
Jean-Baptiste de Villèle, Prime Minister of France (b. 1773)
March 18 – Alexander Allan, Scottish businessman, founder of Allan Line (b. 1780)
March 19 – William Pope Duval, first civilian governor of Florida Territory (b. 1784)
March 21 – Pedro María de Anaya, 2-time President of Mexico (b. 1795)
March 26 – Emilie Hammarskjöld, Swedish-born American musician (b. 1821)
March 27
William Bentinck, 4th Duke of Portland, English politician (b. 1768)
Charles III, Duke of Parma (b. 1823)
April 11 – Karl Adolph von Basedow, German physician (b. 1799)
April 15 – Arthur Aikin, English chemist, mineralogist (b. 1773)
April 22
Nicolás Bravo, 3-time President of Mexico (b. 1786)
April 22 – Domingo Eyzaguirre, Chilean philanthropist (b. 1775)
April 29 – Henry Paget, 1st Marquess of Anglesey, British general (b. 1768)
June 7 – Charles Baudin, French admiral (b. 1784)
June 13 – Rosina Regina Ahles, German actor (b. 1799)


1854 (MDCCCLIV) was a common year starting on Sunday of the Gregorian calendar and a common year starting on Friday of the Julian calendar, the 1854th year of the Common Era (CE) and Anno Domini (AD) designations, the 854th  year of the 2nd millennium, the 54th  year of the 19th century, and the  5th   year of the 1850s decade. As of the start of 1854, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.


The word alfalfa is a Spanish modification of the Arabic word al-faṣfaṣa.


Alfalfa seems to have originated in south-central Asia, and was first cultivated in ancient Iran. According to Pliny (died 79 AD), it was introduced to Greece in about 490 BC when the
Persians invaded Greek territory. Alfalfa cultivation is discussed in the fourth-century AD book Opus Agriculturae by Palladius, stating: "One sow-down lasts ten years. The crop may be cut four or six times a year ... A jugerum of it is abundantly sufficient for three horses all the year ... It may be given to cattle, but new provender is at first to be administered very sparingly, because it bloats up the cattle." Pliny and Palladius called alfalfa in Latin medica, a name that referred to the Medes, a people who lived in ancient Iran. The ancient Greeks and Romans believed, probably correctly, that alfalfa came from the Medes' land, in today's Iran. (The ancient Greeks and Romans also used the name medica to mean a citron fruit, once again because it was believed to have come from the Medes' land). This name is the root of the modern scientific name for the alfalfa genus, Medicago.
The medieval Arabic agricultural writer Ibn al-'Awwam, who lived in Spain in the later 12th century, discussed how to cultivate alfalfa, which he called الفصفصة (al-fiṣfiṣa). A 13th-century general-purpose Arabic dictionary, Lisān al-'Arab, says that alfalfa is cultivated as an animal feed and consumed in both fresh and dried forms. It is from the Arabic that the Spanish name alfalfa was derived.
In the 16th century, Spanish colonizers introduced alfalfa to the Americas as fodder for their horses.
In the North American colonies of the eastern US in the 18th century, it was called "lucerne", and many trials at growing it were made, but generally without sufficiently successful results. Relatively little is grown in the southeastern United States today. Lucerne (or luzerne) is the name for alfalfa in Britain, Australia, France, Germany, and a number of other countries. Alfalfa seeds were imported to California from Chile in the 1850s. That was the beginning of a rapid and extensive introduction of the crop over the western US States and introduced the word "alfalfa" to the English language. Since North and South America now produce a large part of the world's output, the word "alfalfa" has been slowly entering other languages.


Like most plants, alfalfa can be attacked by various pests and pathogens. Diseases often have subtle symptoms which are easily misdiagnosed and can affect leaves, roots, and stems.
Some pests, such as the alfalfa weevil, aphids, armyworms, and the potato leafhopper, can reduce alfalfa yields dramatically, particularly with the second cutting when weather is warmest. Spotted alfalfa aphid, broadly spread in Australia, not only sucks sap but also injects salivary toxins into the leaves. Registered insecticides or chemical controls are sometimes used to prevent this and labels will specify the withholding period before the forage crop can be grazed or cut for hay or silage. Alfalfa is also susceptible to root rots, including Phytophthora, Rhizoctonia, and Texas root rot. Alfalfa is also susceptible to downy mildew caused by the oomycete species Peronospora aestivalis.


Alfalfa (/ælˈfælfə/) (Medicago sativa), also called lucerne, is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world. It is used for grazing, hay, and silage, as well as a green manure and cover crop. The name alfalfa is used in North America. The name lucerne is the more commonly used name in the United Kingdom, South Africa, Australia, and New Zealand. The plant superficially resembles clover (a cousin in the same family), especially while young, when trifoliate leaves comprising round leaflets predominate. Later in maturity, leaflets are elongated. It has clusters of small purple flowers followed by fruits spiralled in 2 to 3 turns containing 10–20 seeds. Alfalfa is native to warmer temperate climates. It has been cultivated as livestock fodder since at least the era of the ancient Greeks and Romans.


Alfalfa is widely grown throughout the world as forage for cattle, and is most often harvested as hay, but can also be made into silage, grazed, or fed as greenchop. Alfalfa usually has the highest feeding value of all common hay crops. It is used less frequently as pasture. When grown on soils where it is well-adapted, alfalfa is often the highest-yielding forage plant, but its primary benefit is the combination of high yield per hectare and high nutritional quality.
Its primary use is as feed for high-producing dairy cows, because of its high protein content and highly digestible fiber, and secondarily for beef cattle, horses, sheep, and goats. Alfalfa hay is a widely used protein and fiber source for meat rabbits. In poultry diets, dehydrated alfalfa and alfalfa leaf concentrates are used for pigmenting eggs and meat, because of their high content in carotenoids, which are efficient for colouring egg yolk and body lipids. Humans also eat alfalfa sprouts in salads and sandwiches. Dehydrated alfalfa leaf is commercially available as a dietary supplement in several forms, such as tablets, powders and tea. Fresh alfalfa can cause bloating in livestock, so care must be taken with livestock grazing on alfalfa because of this hazard.
Like other legumes, its root nodules contain bacteria, Sinorhizobium meliloti, with the ability to fix nitrogen, producing a high-protein feed regardless of available nitrogen in the soil. Its nitrogen-fixing ability (which increases soil nitrogen) and its use as an animal feed greatly improve agricultural efficiency.
Alfalfa can be sown in spring or fall, and does best on well-drained soils with a neutral pH of 6.8–7.5. Alfalfa requires sustained levels of potassium and phosphorus to grow well. It is moderately sensitive to salt levels in both the soil and irrigation water, although it continues to be grown in the arid southwestern United States, where salinity is an emerging issue. Soils low in fertility should be fertilized with manure or a chemical fertilizer, but correction of pH is particularly important. Usually a seeding rate of 13–20 kg/ha (12–18 lb/acre) is recommended, with differences based upon region, soil type, and seeding method. A nurse crop is sometimes used, particularly for spring plantings, to reduce weed problems and soil erosion, but can lead to competition for light, water, and nutrients.
In most climates, alfalfa is cut three to four times a year, but it can be harvested up to 12 times per year in Arizona and southern California. Total yields are typically around 8 tonnes per hectare (3+1⁄2 short tons per acre) in temperate environments, but yields have been recorded up to 20 tonnes per hectare (9 short tons per acre). Yields vary with region, weather, and the crop's stage of maturity when cut. Later cuttings improve yield, but with reduced nutritional content.


Alfalfa is a perennial forage legume which normally lives four to eight years, but can live more than 20 years, depending on variety and climate. The plant grows to a height of up to 1 metre (3 feet 3 inches), and has a deep root system, sometimes growing to a depth of more than 15 m (49 ft) to reach groundwater. Typically the root system grows to a depth of 2–3 m (7–10 ft) depending on subsoil constraints. Owing to this deep root system, it helps to improve soil nitrogen fertility and protect from soil erosion. This depth of root system, and perenniality of crowns that store carbohydrates as an energy reserve, make it very resilient, especially to droughts. Alfalfa has a tetraploid genome.
Alfalfa is a small-seeded crop, and has a slowly growing seedling, but after several months of establishment, forms a tough "crown" at the top of the root system. This crown contains shoot buds that enable alfalfa to regrow many times after being grazed or harvested; however, overgrazing of the buds will reduce the new leaves on offer to the grazing animal.
This plant exhibits autotoxicity, which means it is difficult for alfalfa seed to grow in existing stands of alfalfa. Therefore, alfalfa fields are recommended to be rotated with other species (for example, corn or wheat) before reseeding. The exact mechanism of auto-toxicity is unclear, with medicarpins and phenols both seeming to play a role. Levels of autotoxicity in soil depends on soil type (clay soils maintain autotoxicity for longer), cultivar and age of the previous crop. A soil assay can be used to measure autotoxicity. Resistant to autotoxicity also varies by cultivar, a tolerant one being 'WL 656HQ'.


The United States encouraged settlement of the east side of the Mississippi and removal of Indians to the west. A disputed 1804 treaty between Quashquame and William Henry Harrison (then governor of the Indiana Territory) that surrendered much of Illinois to the U.S. enraged many Sauk and led to the 1832 Black Hawk War.
The Sauk and Meskwaki sold their land in the Mississippi Valley during 1832 in the Black Hawk Purchase and sold their remaining land in Iowa in 1842, most of them moving to a reservation in Kansas. Many Meskwaki later returned to Iowa and settled near Tama, Iowa; the Meskwaki Settlement remains to this day. In 1856 the Iowa Legislature passed an unprecedented act allowing the Meskawki to purchase the land. However, in contrast to the unprecedented act of the Iowa Legislature, the United States Federal Government, through the use of Treaties, forced the Ho-Chunk from Iowa in 1848, and forced the Dakota from Iowa by 1858. Western Iowa around modern Council Bluffs was used as an Indian Reservation for members of the Council of Three Fires.


The first known European explorers to document Iowa were Jacques Marquette and Louis Jolliet who traveled the Mississippi River in 1673 documenting several Indigenous villages on the Iowa side. The area of Iowa was claimed for France and remained a French territory until 1763. The French, before their impending defeat in the French and Indian War, transferred ownership to their ally, Spain. Spain practiced very loose control over the Iowa region, granting trading licenses to French and British traders, who established trading posts along the Mississippi and Des Moines Rivers.
Iowa was part of a territory known as La Louisiane or Louisiana, and European traders were interested in lead and furs obtained by Indigenous people. The Sauk and Meskwaki effectively controlled trade on the Mississippi in the late 18th century and early 19th century. Among the early traders on the Mississippi were Julien Dubuque, Robert de la Salle, and Paul Marin. Along the Missouri River at least five French and English trading houses were built before 1808. In 1800, Napoleon Bonaparte took control of Louisiana from Spain in a treaty.
After the 1803 Louisiana Purchase, Congress divided the Louisiana Purchase into two parts—the Territory of Orleans and the District of Louisiana, with present-day Iowa falling in the latter. The Indiana Territory was created in 1800 to exercise jurisdiction over this portion of the District; William Henry Harrison was its first governor. Much of Iowa was mapped by Zebulon Pike in 1805, but it was not until the construction of Fort Madison in 1808 that the U.S. established tenuous military control over the region.


Iowa (/ˈaɪoʊwə/ (listen)) is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to the east and southeast, Missouri to the south, Nebraska to the west, South Dakota to the northwest, and Minnesota to the north.
During the 18th and early 19th centuries, Iowa was a part of French Louisiana and Spanish Louisiana; its state flag is patterned after the flag of France. After the Louisiana Purchase, people laid the foundation for an agriculture-based economy in the heart of the Corn Belt. In the latter half of the 20th century, Iowa's agricultural economy transitioned to a diversified economy of advanced manufacturing, processing, financial services, information technology, biotechnology, and green energy production.
Iowa is the 26th most extensive in total area and the 31st most populous of the 50 U.S. states, with a population of 3,190,369, according to the 2020 census. The state's capital, most populous city, and largest metropolitan area fully located within the state is Des Moines. A portion of the larger Omaha, Nebraska, metropolitan area extends into three counties of southwest Iowa. Iowa has been listed as one of the safest U.S. states in which to live.


Poor labor conditions and discontent among miners resulted in several major clashes between strikers and the Colorado National Guard, including the 1903–1904 Western Federation of Miners Strike and Colorado Coalfield War, the latter of which included the Ludlow massacre that killed a dozen women and children. Both the 1913–1914 Coalfield War and the Denver streetcar strike of 1920 resulted in federal troops intervening to end the violence. In 1927, the Columbine Mine massacre resulted in six dead strikers following a confrontation with Colorado Rangers. More than 5,000 Colorado miners—many immigrants—are estimated to have died in accidents since records began to be formally collected following an accident in Crested Butte that killed 59 in 1884.
In 1924, the Ku Klux Klan Colorado Realm achieved dominance in Colorado politics. With peak membership levels, the Second Klan levied significant control over both the local and state Democrat and Republican parties, particularly in the governor's office and city governments of Denver, Cañon City, and Durango. A particularly strong element of the Klan controlled the Denver Police. Cross burnings became semi-regular occurrences in cities such as Florence and Pueblo. The Klan targeted African-Americans, Catholics, Eastern European immigrants, and other non-White Protestant groups. Efforts by non-Klan lawmen and lawyers including Philip Van Cise lead to a rapid decline in the organization's power, with membership waning significantly by the end of the 1920s.
Colorado became the first western state to host a major political convention when the Democratic Party met in Denver in 1908. By the U.S. Census in 1930, the population of Colorado first exceeded one million residents. Colorado suffered greatly through the Great Depression and the Dust Bowl of the 1930s, but a major wave of immigration following World War II boosted Colorado's fortune. Tourism became a mainstay of the state economy, and high technology became an important economic engine. The United States Census Bureau estimated that the population of Colorado exceeded five million in 2009.
On September 11, 1957, a plutonium fire occurred at the Rocky Flats Plant, which resulted in the significant plutonium contamination of surrounding populated areas.
From the 1940s and 1970s, many protest movements gained momentum in Colorado, predominantly in Denver. This included the Chicano Movement, a civil rights and social movement of Mexican Americans emphasizing a Chicano identity that is widely considered to have begun in Denver. The First National Chicano Liberation Youth Conference was held in Colorado in March 1969.
In 1967, Colorado was the first state to loosen restrictions on abortion when governor John Love signed a law allowing abortions in cases of rape, incest, or threats to the woman's mental or physical health. Many states followed Colorado's lead in loosening abortion laws in the 1960s and 1970s.
Since the late 1990s, Colorado has been the site of multiple major mass shootings, including the infamous Columbine High School massacre in 1999 which made international news, where Eric Harris and Dylan Klebold killed 12 students and one teacher, before committing suicide. The incident has since spawned many copycat incidents. On July 20, 2012, a gunman killed 12 people in a movie theater in Aurora. The state responded with tighter restrictions on firearms, including introducing a limit on magazine capacity. On March 22, 2021, a gunman killed 10 people, including a police officer, in a King Soopers supermarket in Boulder.
Four warships of the U.S. Navy have been named the USS Colorado. The first USS Colorado was named for the Colorado River and served in the Civil War and later the Asiatic Squadron, where it was attacked during the 1871 Korean Expedition. The later three ships were named in honor of the state, the including an armored cruiser and the battleship USS Colorado, the latter of which was the lead ship of her class and served in World War II in the Pacific beginning in 1941. At the time of the attack on Pearl Harbor, the battleship USS Colorado was located at the naval base in San Diego, California, and thus went unscathed. The most recent vessel to bear the name USS Colorado is Virginia-class submarine USS Colorado (SSN-788), which was commissioned in 2018.


Approximately half of Colorado is flat and rolling land. East of the Rocky Mountains are the Colorado Eastern Plains of the High Plains, the section of the Great Plains within Nebraska at elevations ranging from roughly 3,350 to 7,500 feet (1,020 to 2,290 m). The Colorado plains are mostly prairies but also include deciduous forests, buttes, and canyons. Precipitation averages 15 to 25 inches (380 to 640 mm) annually.
Eastern Colorado is presently mainly farmland and rangeland, along with small farming villages and towns. Corn, wheat, hay, soybeans, and oats are all typical crops. Most villages and towns in this region boast both a water tower and a grain elevator. Irrigation water is available from both surface and subterranean sources. Surface water sources include the South Platte, the Arkansas River, and a few other streams. Subterranean water is generally accessed through artesian wells. Heavy usage of these wells for irrigation purposes caused underground water reserves to decline in the region. Eastern Colorado also hosts a considerable amount and range of livestock, such as cattle ranches and hog farms.


Colorado is notable for its diverse geography, which includes alpine mountains, high plains, deserts with huge sand dunes, and deep canyons. In 1861, the United States Congress defined the boundaries of the new Territory of Colorado exclusively by lines of latitude and longitude, stretching from 37°N to 41°N latitude, and from 102°02′48″W to 109°02′48″W longitude (25°W to 32°W from the Washington Meridian). After 161 years of government surveys, the borders of Colorado were officially defined by 697 boundary markers and 697 straight boundary lines. Colorado, Wyoming, and Utah are the only states that have their borders defined solely by straight boundary lines with no natural features. The southwest corner of Colorado is the Four Corners Monument at 36°59′56″N, 109°2′43″W. The Four Corners Monument, located at the place where Colorado, New Mexico, Arizona, and Utah meet, is the only place in the United States where four states meet.


The region that is today the State of Colorado has been inhabited by Native Americans and their Paleoamerican ancestors for at least 13,500 years and possibly more than 37,000 years. The eastern edge of the Rocky Mountains was a major migration route that was important to the spread of early peoples throughout the Americas. The Lindenmeier site in Larimer County contains artifacts dating from approximately 8720 BCE. The Ancient Pueblo peoples lived in the valleys and mesas of the Colorado Plateau. The Ute Nation inhabited the mountain valleys of the Southern Rocky Mountains and the Western Rocky Mountains, even as far east as the Front Range of the present day. The Apache and the Comanche also inhabited Eastern and Southeastern parts of the state. In the 17th century, the Arapaho and Cheyenne moved west from the Great Lakes region to hunt across the High Plains of Colorado and Wyoming.
The Spanish Empire claimed Colorado as part of its New Mexico province before U.S. involvement in the region. The U.S. acquired a territorial claim to the eastern Rocky Mountains with the Louisiana Purchase from France in 1803. This U.S. claim conflicted with the claim by Spain to the upper Arkansas River Basin as the exclusive trading zone of its colony of Santa Fe de Nuevo México. In 1806, Zebulon Pike led a U.S. Army reconnaissance expedition into the disputed region. Colonel Pike and his men were arrested by Spanish cavalrymen in the San Luis Valley the following February, taken to Chihuahua, and expelled from Mexico the following July.
The U.S. relinquished its claim to all land south and west of the Arkansas River and south of 42nd parallel north and west of the 100th meridian west as part of its purchase of Florida from Spain with the Adams-Onís Treaty of 1819. The treaty took effect on February 22, 1821. Having settled its border with Spain, the U.S. admitted the southeastern portion of the Territory of Missouri to the Union as the state of Missouri on August 10, 1821. The remainder of Missouri Territory, including what would become northeastern Colorado, became an unorganized territory and remained so for 33 years over the question of slavery. After 11 years of war, Spain finally recognized the independence of Mexico with the Treaty of Córdoba signed on August 24, 1821. Mexico eventually ratified the Adams–Onís Treaty in 1831. The Texian Revolt of 1835–36 fomented a dispute between the U.S. and Mexico which eventually erupted into the Mexican–American War in 1846. Mexico surrendered its northern territory to the U.S. with the Treaty of Guadalupe Hidalgo after the war in 1848.
Most American settlers traveling overland west to the Oregon Country, the new goldfields of California, or the new Mormon settlements of the State of Deseret in the Salt Lake Valley, avoided the rugged Southern Rocky Mountains, and instead followed the North Platte River and Sweetwater River to South Pass (Wyoming), the lowest crossing of the Continental Divide between the Southern Rocky Mountains and the Central Rocky Mountains. In 1849, the Mormons of the Salt Lake Valley organized the extralegal State of Deseret, claiming the entire Great Basin and all lands drained by the rivers Green, Grand, and Colorado. The federal government of the U.S. flatly refused to recognize the new Mormon government, because it was theocratic and sanctioned plural marriage. Instead, the Compromise of 1850 divided the Mexican Cession and the northwestern claims of Texas into a new state and two new territories, the state of California, the Territory of New Mexico, and the Territory of Utah. On April 9, 1851, Mexican American settlers from the area of Taos settled the village of San Luis, then in the New Mexico Territory, later to become Colorado's first permanent Euro-American settlement.
In 1854, Senator Stephen A. Douglas persuaded the U.S. Congress to divide the unorganized territory east of the Continental Divide into two new organized territories, the Territory of Kansas and the Territory of Nebraska, and an unorganized southern region known as the Indian territory. Each new territory was to decide the fate of slavery within its boundaries, but this compromise merely served to fuel animosity between free soil and pro-slavery factions.
The gold seekers organized the Provisional Government of the Territory of Jefferson on August 24, 1859, but this new territory failed to secure approval from the Congress of the United States embroiled in the debate over slavery. The election of Abraham Lincoln for the President of the United States on November 6, 1860, led to the secession of nine southern slave states and the threat of civil war among the states. Seeking to augment the political power of the Union states, the Republican Party-dominated Congress quickly admitted the eastern portion of the Territory of Kansas into the Union as the free State of Kansas on January 29, 1861, leaving the western portion of the Kansas Territory, and its gold-mining areas, as unorganized territory.


The United States Congress passed an enabling act on March 3, 1875, specifying the requirements for the Territory of Colorado to become a state. On August 1, 1876 (four weeks after the Centennial of the United States), U.S. President Ulysses S. Grant signed a proclamation admitting Colorado to the Union as the 38th state and earning it the moniker "Centennial State".
The discovery of a major silver lode near Leadville in 1878 triggered the Colorado Silver Boom. The Sherman Silver Purchase Act of 1890 invigorated silver mining, and Colorado's last, but greatest, gold strike at Cripple Creek a few months later lured a new generation of gold seekers. Colorado women were granted the right to vote on November 7, 1893, making Colorado the second state to grant universal suffrage and the first one by a popular vote (of Colorado men). The repeal of the Sherman Silver Purchase Act in 1893 led to a staggering collapse of the mining and agricultural economy of Colorado, but the state slowly and steadily recovered. Between the 1880s and 1930s, Denver's floriculture industry developed into a major industry in Colorado. This period became known locally as the Carnation Gold Rush.