Meriwether Lewis

 It was on this day in 1803 that President Thomas Jefferson sent a formal letter to his private secretary and aide, Meriwether Lewis.
 
Lewis was a captain in the first United States infantry. Jefferson wrote him to request that he might lead an expedition of the Missouri River.

Jefferson never mentioned botany in the letter, but he clearly was thinking about it, and Lewis knew it.

As he was preparing for his trip, Lewis connected with Benjamin Smith Barton. Barton had written the first American textbook on botany and he gave Lewis a little crash course on the subject.