Lewis and Clark expedition

US government expedition conducted 1804–06 to map uncharted territory bought from France under the Louisiana Purchase (1803), and to find a land route to the Pacific coast. The survey, ordered by President Thomas Jefferson, was led by Meriwether Lewis and William Clark. The round trip from St Louis, Missouri to the mouth of the Columbia River covered some 13,000 km/8,000 mi. Information gathered by the explorers, and the opening of a new route to the Pacific, helped to fuel the Westward expansion of the USA; one immediate effect was an influx of US mountain men (fur traders) to the Rocky Mountain regions. The Lewis and Clark National Historic Trail, opened in 1978, marks the route taken by the explorers.

The expedition followed the Missouri River northwest from St Louis to the Three Forks in western Montana. From there, they took the Jefferson River southwest to its head, crossed the Continental Divide at Lemhi Pass, traversed the Bitterroot Range at Lolo Pass, descended the Clearwater River to the Snake (originally Lewis) River; followed the Snake to the Columbia River; and finally rafted down the Columbia to the Pacific, ending their journey at Oregon's Fort Clatsop. On their return east, the explorers also investigated the routes taken by the Marias and Yellowstone rivers, in Montana.

Lewis, an experienced hunter and forester, was the president's private secretary, while Clark was a friend of Lewis. President Jefferson had paid $15 million dollars for a vast area of land (the present-day states of Louisiana, Missouri, Arkansas, Iowa, Nebraska, North Dakota, South Dakota, and Oklahoma), and wanted to discover what had been bought. The surveyors were asked to chart the country's layout, as well as record information about its weather, soil, animals, plants, and American Indian inhabitants. It was also hoped that they would map out a land route to the Pacific coast, north of the territory held by Spain.

Lewis and Clark left St Louis on 4 May 1804 with a team of 27, including French and Kentuckians. They reached North Dakota in late autumn and built Fort Mandan where they wintered until the spring. When they began their trek again, they were joined by Toussant Charbonneau and his wife Sacajewea, a Shoshone Indian, who became their interpreters and guides.

The surveyors had heard many myths about the land, including the existence of vicious Amazonian women, tiny 46-cm/18-in devils, and Welsh-speaking Indians. None of these proved true. Instead they discovered over 50 American Indian groups, most of whom were willing to establish a friendly relationship; herds of buffalo, elk, and antelope; hordes of mosquitoes; and unusual plants. They also came across rattlesnakes and grizzly bears, and experienced harsh winters. However, during the entire journey, only one person died (because of a ruptured appendix). The expedition returned to St Louis on 23 September 1806.