-Fricken author of the Constitution (most major contributor)
-Louisiana Purchase from Napoleon
-Killed the national bank
-Spearheaded the philosophy of freedom and many other libertarian-type ideals, many that are looked up to and sought today.
-Built and designed the University of Virginia.
Not many people know this, but Jefferson was the first American anthropologist. In addition, he was a farmer, architect, lawyer, among other things. He wasn't just practicing these fields, he contributed to innovating them too. For farming, he designed the moldboard plow. He was fluent in five different languages. Incredibly learned man. Knew his history, literature, and economics. His library was considered legendary at the time for a single person. I haven't even touched on his contributions to religious freedom. In terms of American enlightenment, only Benjamin Franklin can hold a candle against him, but he was never a president... The standard this guy sets when it comes to intellectualism is unreal and I don't think we will ever see a president like him (at least in my lifetime).
while I agree that its clearly jefferson, he was not the first american anthropologist. an argument can be made that he was one of the first american archaeologists, but the first american "anthropologist" has him beat by a couple hundred years (Cabeza de Vaca).