As he helped lead the Corps of Discovery across the continent, Meriwether Lewis spent hours collecting, preserving, and describing the numerous unfamiliar plants he found along the route. Lewis had little academic training as a botanist, but he was fortunate to have gained experience with plants from a number of sources. His mother, Lucy Marks, was an herbalist. His close friend, Thomas Jefferson, possessed numerous botanical books, and was constantly experimenting with new plants in his gardens. Lewis also trained for a brief period with Benjamin Smith Barton, author of the first botanical textbook printed in the United States.

After he returned from the expedition, Lewis loaned his pressed plant specimens to Benjamin Smith Barton, with hopes that he would write an account of the botanical discoveries of the expedition. The volume was never completed, but in 1814 Frederick Pursh used Lewis's specimens for descriptions in his own work Flora Americae Septentrionalis. The image at the left of the bitteroot (Clarkia pulchella) is an illustration of one of Lewis's specimens as drawn by Pursh. Today most of the original plant specimens are preserved at the Academy of Natural Sciences in Philadelphia.