Jesse James and Little Archie Clements
The man on the left is Jesse, and the man on the right is his closest friend during the Civil War, Little Archie Clements. This photo was taken in either 1864 or 1865. This is the only photo where Jesse's left hand is showing, so it was taken before he lost the tip of his middle left finger.
Jesse James, post-Civil War guerrilla
This photo was probably taken around the same time as the previous photo.