Spanish navigators seeking a passage from the Moluccas to South America are the first Europeans known to have sighted land in the eastern half of the island of New Guinea. In 1528-29, Alvaro de Saavedra sailed along the north coast and seems to have reached the Admiralty Islands. In 1545, Iñigo Ortiz de Retes also sailed eastwards along the north coast, possibly as far as Astrolabe Bay. Luis Vaez Torres sailed along the south coast in 1606 and established that there was a strait (now named for him) between New Guinea and Australia. In 1616, a Dutch expedition led by Willem Schouten and Jacob le Maire rounded Cape Horn, crossed the Pacific, identified New Ireland and other islands in that vicinity and passed westward along the north coast. In 1700, the British explorer William Dampier established that New Britain was an island separated from New Guinea by sailing through the strait which now bears his name. In 1767, another English navigator, Philip Carteret, explored the passage between New Britain and New Ireland, and gave the Admiralty Islands their present name. French navigators Louis Antoine de Bougainville (1768) and Bruni d’Entrecasteaux (1793) mapped extensive sections of the mainland coast and islands to the east. In the 19th century British naval captains Francis Blackwood and Charles Yule (1842), Owen Stanley (1848) and John Moresby (1873) completed the basic charting of PNG waters.
The first European to move successfully inland was probably the Italian naturalist and explorer Luigi Maria d’Albertis, who spent six weeks traveling up the Fly River in 1876. Exploration of the inland by the British colonial Administration patrols was pioneered by William MacGregor (1888-98). MacGregor did much of the exploration himself and discouraged private explorers. He traveled part of the way up all main rivers, climbed the major peaks of the central mountain chain and explored many off-shore islands. Other expeditions were undertaken by members of MacGregor’s staff such as John Green and C.A.W. Monckton. By 1900 gold prospectors had also investigated sections of some inland rivers in Papua. Further areas were explored by gold prospectors in the 1920s.
Much exploration for the purpose of extending Administration control was undertaken during the term of office of Sir Hubert Murray 1908-40. Major well-organized expeditions were conducted in the 1920s and 1930s. Murray planned to send patrols into the northwest of the Territory until Papua was fairly well known and then send a party to attempt a crossing to the coast of German New Guinea. In a major journey in 1927-28, C. Karius and I.F. Champion spent four months crossing from the Fly River to the Sepik River. In 1935, J. G. Hides and L.J. O’Malley followed the Strickland River into the well populated southern highlands. In 1936 and 1937 expeditions led by Ivan Champion reached Mount Hagen and Lake Kutubu. By 1939 Murray believed that the whole of Papua had been explored. This was not entirely correct. It was not until the 1950s that Administration patrols reached parts of the southern highlands.
In German New Guinea (1884-1914) the first expeditions were sponsored by scientific institutions and private companies. In 1887, an astronomer, C. Schrader, accompanied by a botanist and geologist, traveled up the Sepik River. In 1888, a journalist, H. Zoller, explored inland from Astrolabe Bay to the Finisterre Ranges. In 1885, Otto von Ehlers died in an attempt to walk from (the present) Salamaua to the south coast. From 1907 to 1913 German scientific bodies mounted major expeditions which investigated the upper Ramu River, the lower Bismarck ranges, Aitape, Huon Gulf and Markham River. These parties, which were well equipped and included leading naturalists and anthropologists, often spent long periods in the area in which they were working. The last German scientific expedition was in the Sepik River region in 1912-13. Missionaries explored parts of New Britain and Bougainville Islands. When Australia took over the colony after World War I, exploration was mainly for the purpose of extending Administration control or gold prospecting. In the mid-1920s gold mining took Australians into the Wau-Bulolo area.
From colonization in 1884 to the 1920s Europeans ignored the center of PNG because they assumed that it would be rugged, mountainous, sparsely populated country. A few missionary and prospecting parties reached the edge of the highlands in the late 1920s. In 1933, Michael and Daniel Leahy flew over the Chimbu and Waghi valleys and reported vast areas of fertile, densely populated land. Extensive Administration patrols into the highlands were led by the Leahy brothers and James Taylor in 1933, and Taylor and Black in 1938. Further exploration parties were sent in during the second half of the 1930s, but it was not until the 1950s that the Administration was confident that all people in the highlands had been contacted.