The United States purchased the area around the Great Falls of the Missouri from France (which claimed the area despite Native American habitation) in 1803, as part of the Louisiana Purchase. Thomas Jefferson, then President of the United States, had long desired to send an expedition into the area. Jefferson sought and won permission and funding for an expedition from Congress in January 1803. On May 14, 1804, the Lewis and Clark Expedition departed St. Louis, Missouri to map the course of the Missouri River; establish whether a river route to the Pacific Ocean existed; study the Indian tribes, botany, geology, terrain and wildlife in the region; and evaluate whether British and French Canadian hunters and trappers in the area posed a challenge to American control over the region. Expedition leaders Meriwether Lewis and William Clark first learned of the "great falls" from the Mandan Indians while wintering at Fort Mandan from November 2, 1804, until April 7, 1805.