The Lewis and Clark Expedition (1804-1806)

This map is part of a series of 20 animated maps showing the history of The United States: a territorial history.

Following the Louisiana Purchase in 1803, President Jefferson sent Lewis, his personal secretary, and Captain Clark on a scientific, political and commercial mission of exploration westwards to the Pacific Ocean.

Lewis and Clark set out with 40 men, leaving Saint Louis in May 1804 and following the Mississippi across Sioux territory. They spent the first winter from November to April with the Mandan Indians.

By mid-June, the travellers had reached the Missouri Falls, just as the Indians had told them.

During the summer, Lewis and Clark borrowed horses from the Shoshone Indians and left the Missouri basin. They crossed the Continental Divide and began their descent to the ocean following rivers in the Columbia basin, reaching the Pacific coast in December 1805.

They spent their second winter there and began their return journey on March 23,1806. The trip up the Columbia River proved to be exhausting, forcing Lewis and Clark to leave the canoes and continue on horseback.

In July, the expedition party separated into two groups: Lewis explored the Marias River to the North, while Clark travelled south along the Yellowstone River.

The two groups met up as they travelled down the Missouri and arrived in Saint Louis on September 23, 1806.

From their travels, Lewis and Clark brought back a considerable quantity of geographical and scientific information and confirmed the presence of Indians throughout the continent.