In 1803, while the United States was negotiating the purchase of the Louisiana Territory from France, President Thomas Jefferson sent a confidential message to Congress proposing exploration of the region. Mindful of Congress’s authority to regulate commerce, Jefferson emphasized the need for better knowledge about American Indians of the Northwest in order to develop trade. Congress authorized and funded an expedition led by Meriwether Lewis and William Clark. An 1806 report to Congress with data gathered by Lewis and Clark confirmed the territory’s commercial potential.
In all your intercourse with the natives, . . . make them acquainted with the position, extent character, peaceable & commercial dispositions of the US . . . & of our dispositions to a commercial intercourse with them
Thomas Jefferson, Instructions to Meriwether Lewis, June 20, 1803