Agriculture is a major industry in the United States, which is a net exporter of food. As of the 2007 census of agriculture, there were 2.2 million farms, covering an area of 922 million acres (3,730,000 km2), an average of 418 acres (1.69 km2) per farm. Although agricultural activity occurs in most states, it is particularly concentrated in the Great Plains, a vast expanse of flat, arable land in the center of the United States and in the region around the Great Lakes known as the Corn Belt.
The United States was a leader in seed improvement i.e. hybridization and in expanding uses for crops from the work of George Washington Carver to the development of bioplastics and biofuels. The mechanization of farming, intensive farming, has been a major theme in U.S. history, including John Deere’s steel plow, Cyrus McCormick’s mechanical reaper, Eli Whitney’s cotton gin to the widespread success of the Fordson tractor and the combine harvesters first made from them. Modern agriculture in the U.S. ranges from the common hobby farms, small-scale producers to large commercial farming covering thousands of acres of cropland or rangeland.
European agricultural practices greatly affected the New England landscape. Colonists brought livestock over from Europe which caused many changes to the land. Grazing animals required a lot of land and food and the act of grazing itself destroyed native grasses, which were being replaced by European species. New species of weeds were introduced and began to thrive as they were capable of withstanding the grazing of animals, whereas native species could not.
In the United States, farms spread from the colonies westward along with the settlers. In cooler regions, wheat was often the crop of choice when lands were newly settled, leading to a “wheat frontier” that moved westward over the course of years. Also very common in the antebellum Midwest was farming corn while raising hogs, complementing each other especially since it was difficult to get grain to market before the canals and railroads. After the “wheat frontier” had passed through an area, more diversified farms including dairy cattle generally took its place. Warmer regions saw plantings of cotton and herds of beef cattle. In the early colonial south, raising tobacco and cotton was common, especially through the use of slave labor until the Civil War. In the northeast, slaves were used in agriculture until the early 19th century. In the Midwest, slavery was prohibited by the Freedom Ordinance of 1787.