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The Lewis and Clark Expedition did not take place in vacuum. It occurred because of President Thomas Jefferson's long fascination with the western lands and his vision for the young United States. Objectives to achieve that vision focused on economic and security concerns. One strategy involved acquisition of American Indian lands within the borders of the U.S. so that Americans could have more land on which to settle. The expedition was another strategy for achieving the objectives.
A document which addresses both strategies is Jefferson's confidential message to Congress, January 18, 1803, which resulted in the authorization of the Lewis and Clark Expedition (Jackson, 1:10-14). The message was related to reauthorizing trading posts for Indian tribes, and it served as a useful vehicle for proposing this American voyage of discovery.
In that message, Jefferson first makes the case to Congress that Indians must be enticed to assimilate and become part of the U.S. He cites the following reasons for action:
growing Indian unrest regarding land sales,
the need for Indians to abandon hunting and assume domestic occupations requiring less land, and
the need to increase government trading posts to drive out for-profit commercial traders.
Jefferson then proposes an expedition to explore the Missouri River to the Western ocean, "the only line of easy communication across the continent." He cites as benefits:
the Indian tribes and their extensive fur trade,
the possibility of "conferences with the natives on the subject of commercial intercourse," and
admission of American traders to the area.
He notes that the geographical knowledge gained will "be an additional gratification."
On February 27, 1803, the day before Congress approved the expedition, Jefferson wrote a private letter to William Henry Harrison, Governor of Indiana Territory. Jefferson laid out his policy with regard to American Indians in similar terms to the message to Congress but more bluntly. He feels this system "will best promote the interests of the Indians & of ourselves, & finally consolidate our whole country into one nation only." He tells Harrison that they must concentrate on "the purchase and settlement of the country on the Missisipi from it's mouth to it's Northern regions, that we may be able to present as strong a front on our Western as on our Eastern border." Jefferson indicates that he has sent Harrison the authority to conclude treaties with the Indians in the Indiana Territory and tells him to move quickly to obtain any land possible (Clanin, Reel 1, pp. 519-24).
Part of Jefferson's concern was the situation in the Spanish territory of Louisiana on the western border of the U.S., which was about to be occupied by the French. The U.S. purchase of Louisiana from the French in the spring of 1803 provided a major impetus to Jefferson's vision.
The map on this page demonstrates how well Harrison accomplished Jefferson's order in the Indiana Territory. At the same time, the Lewis and Clark Expedition solidified the U.S. ownership of the territory of Louisiana, explored the western lands that would later become part of the U.S., and gathered extraordinary scientific information.
After the return of the expedition, Lewis was appointed governor of the Territory of Louisiana, and Clark was appointed superintendent of Indian affairs for that same territory. At that time, Harrison was still governor of Indiana Territory. All three men continued to be agents of Jefferson's policy to extinguish the land claims of American Indians and to protect the U.S. from foreign aggression.
Jefferson's vision, however, underestimated the desire of Americans to work and live in the lands to the west and the resistance to assimilation among most Indians. Harrison's Treaty of Fort Wayne in 1809 added to the increasing unrest among the Indians and strengthened the efforts of Tecumseh and the Prophet to unify the Indian tribes against the Americans.