And that, of course, left the post of naturalist to be filled. And as I mentioned, that search included discussion with William Bartram and Rafinesque. Alexander Wilson was extremely desirous of having the post of naturalist on the expedition, and through William Bartram he tendered a letter of application to Jefferson in February of 1806; sat around on pins and needles during the spring of 1806 waiting for a reply from Jefferson, which never came.
And in fact, Wilson's biographer accused Jefferson of disgracing himself by never bothering to respond to Alexander Wilson's letter of application. I've looked for Wilson's letter of application in the Jefferson letters, and never found it. I have found Bartram's letter of introduction, but Wilson's letter is not there, and I really wonder if Jefferson ever got it. In any case, by the time Wilson's letter of application arrived Jefferson had already selected a naturalist for the party.
His name was Peter Custis. He was a last-year medical student at the University of Pennsylvania, working under Benjamin Smith Barton, who was the most famous botanist in America at the time, and who was another one of those savants who had helped Meriwether Lewis prepare for the western expedition up the Missouri.
Benjamin Smith Barton was only thirty-seven years of age. He had considered possibly going on one of these expeditions, but decided he couldn't do it, and so he finally suggested what was one of his top students in the program at Pennsylvania, young Peter Custis, who was from Jefferson's home county, Albemarle County in Virginia—that was Meriwether Lewis's home county as well. Custis also was from a very prominent family in Virginia that was related to the Lees and the Randolphs and also even to President Washington. George Washington's wife, Martha Custis, had been married to a Custis before she married George Washington.
Jefferson didn't seem to know him personally and wrote that "I hope we've acquired a good naturalist." What they acquired in Peter Custis seems to have been a young fellow who had superior scientific skills—he's the first academically trained American naturalist to explore in the West. But he didn't seem to have had any field experience up to this time. And as a result of that lack of field experience, and possibly as a result of some of the sources he took with him to identify plants in the field, he did experience some problems. But he was definitely the best-trained American to accompany an exploring expedition during this entire age. So he's kind of a foundation figure in American science in the West.