The culprit: a Boston baseball player in 1886.
The finger-giver is Charles Radbourn, a pitcher for The Boston Beaneaters. He's giving the finger to the opposing team, the New York Giants. Charles is an interesting figure in his own right; he pitched a whopping 678 2/3 innings, and the leg cramp known as the Charley Horse may be named after him. He died, as most great baseball players do, after a long battle with syphilis.