This is a picture of Allan Pinkerton on Horseback. It was taken on the Antietam Battlefield in 1862. Pinkerton was a body guard for President Lincoln, and actually foiled an assassination attempt on Lincoln in 1861. After the war, Pinkerton founded the famed Pinkerton Detective Agency, and chased outlaws like Jesse James and Cole Younger. He died in 1884 from an infection resulting from him biting his tongue.