What was the purpose of Lewis and Clark's expedition?

Answer 1

or as a shorter answer lol, the lewis and clark expidition, sent by jefferson, was to map the territroy bought from the french in the louisianna purchase
they were also supposed to make pacts and such with indians they met on the way, to ensure good relations with them for a while

Answer 2

Thomas Jefferson had long considered the project of a western expedition, having encouraged John Ledyard when he proposed such an expedition in the 1780s, and as president he contemplated the matter in earnest and discussed it with his private secretary, Capt. Meriwether Lewis. When Congress approved the plan in 1803 and appropriated money for it, Jefferson named Lewis to head it, and Lewis selected William Clark as his associate in command. The purpose was to search out a land route to the Pacific, to strengthen American claims to Oregon territory, and to gather information about the indigenous inhabitants and the country of the Far West. Before the long march was begun, the Louisiana Purchase was made, increasing the need for a survey of the West."

or

"President Thomas Jefferson soft-pedaled the scientific aspects of the expedition when he asked Congress for money in 1803. The purposes of the expedition were twofold, Jefferson claimed, but only the first purpose was of any real consequence - the diplomatic mission of contacting Indian nations, establishing the United States as sovereign over the region and as a major player in the fur trade. He made the second purpose, the scientific one, seem like an inconsequential afterthought. Jefferson knew that diplomacy, especially with the goal of increased commerce, could be sold to Congress; scientific discovery and description could not. One seemed practical, the other less so."

or

"On the acquisition of Louisiana, in the year 1803, the attention of the government of the United States, was early directed towards exploring and improving the new territory. Accordingly in the summer of the same year, an expedition was planned by the president for the purpose of discovering the courses and sources of the Missouri, and the most convenient water communication thence to the Pacific ocean. His private secretary captain Meriwether Lewis, and captain William Clarke, both officers of the army of the United States, were associated in the command of this enterprise. After receiving the requisite instructions, captain Lewis left the seat of government, and being joined by captain Clarke at Louisville, in Kentucky, proceeded to St. Louis, where they arrived in the month of December."