Thomas Jefferson was the third President of the United States, serving from 1801 until 1809. He was a founding father of the country, and wrote the Declaration of Independence during the American Revolution in 1776.
He wears a brown vest with a white undershirt. He has long brown hair. Like many of the characters seen in Cartman's flashback, he curiously was not drawn with normal South Park facial features, instead having realistic facial proportions.
He is obviously extremely patriotic, agitating for war against the British in order to secure independence for the newly-formed United States of America.