Thomas Jefferson commissioned the Lewis and Clark Expedition in 1803 to explore the northwest territory in order to observe a transcontinental route and natural resources. In 1804, about 45 men headed by Meriwether Lewis and William Clark moved up the Missouri River, crossed the Rocky Mountains, and from the Columbia River, reached the Pacific Ocean by November 1805. They returned to St. Louis by September 1806 with great fanfare and important information on native people, plants and animals, and geography.
The Louisiana Purchase (1803)  was a land deal between the United States and France, in which the U.S. acquired approximately 827,000 square miles of land west of the Mississippi River for $15 million dollars.
"This little event, of France's possessing herself of Louisiana, is the embryo of a tornado which will burst on the countries on both sides of the Atlantic and involve in it's effects their highest destinies."
[post January 23, 1793]
To Mr. Andrew Michaud.
Sundry persons having subscribed certain sums of money for your encouragement to explore the country a[long] the Missouri, & thence Westwardly to the Pacific ocean, having submitted the plan of the enterprise to the direction of the American Philosophical society, & the Society having accepted of the trust, they proceed to give you the following instructions.
As Jefferson groomed Meriwether Lewis to head an expedition to explore the West, it was understandable that he would turn to fellow members of the American Philosophical Society for support. This was the oldest learned society in the United States, and one dedicated to furthering knowledge of the natural sciences as well as cultivating the arts.
Barton, Benjamin Smith.Elements of Botany; or, Outlines of the Natural History of Vegetables (Philadelphia, 1803).
Kelly, Patrick.A Practical Introduction to Spherics and Nautical Astronomy; being an attempt to simplify those.sciences. Containing.the discovery of a projection for clearing the lunar distances in order to find the longitude at sea. (London, 1796).