John Wilkes Booth

John Wilkes Booth was the man who plotted and executed the murder of President Abraham Lincoln. The reason for this murder was that

Lincoln allowed voting rights to recently emancipated slaves, which John and co-conspirators did not appreciate. He fled, eventually reaching the Garrett farm, where he was fatally shot in the neck by Sergeant Boston Corbett and died three hours later.  However, there had been theories that Booth faked his own death and fled to South America. 

In the Assassin's Creed Universe, he was

a member of the Templars. It is therefore possible Sergeant Corbett, and even President Lincoln himself, may have been assassins or were affiliated with them.