Lewis and Clark Expedition departs Camp Dubois up the Missouri (1804)

Background. President Thomas Jefferson commissioned the Corps of Discovery in 1803 to explore the newly acquired Louisiana Purchase. Meriwether Lewis was appointed leader, and William Clark joined as co-commander. The expedition's initial staging ground, Camp Dubois, was established in December 1803 on the east side of the Mississippi River. This location ensured the camp remained within United States territory, as the formal transfer of the Louisiana Purchase from France to the U.S. did not occur until March 10, 1804.

Leadership. Meriwether Lewis, an American explorer and soldier, was named the leader of the Corps of Discovery. He invited William Clark, age 33, to share command. Clark's primary home until 1803 was Mulberry Hill, a plantation near Louisville, Kentucky, where he had settled in 1785. Their mission was to explore the territory, establish trade with Native Americans, and consolidate U.S. sovereignty over the region.

Geopolitical Context. The expedition's departure occurred shortly after the 1803 Louisiana Purchase doubled the size of the United States. The transfer of the territory from Spain to France, and then to the U.S., was finalized in March 1804. In March 1804, Spanish authorities in New Mexico learned from General James Wilkinson that Americans were encroaching on territory claimed by Spain. This prompted the Spanish to send armed expeditions in August 1804 to intercept the Corps of Discovery.