The Fifth Face on Mt. Rushmore

When I went to Mount Rushmore this summer, I took a lot of pictures. It is an amazing place and truly fascinating how these guys managed to carve out these massive monuments to four presidents.
Or, wait. Maybe there were five.
I think they gave us four definite faces – Washington, Roosevelt, Jefferson and Lincoln. But then they carved a fifth one and left it optional. Or maybe the crew was just monkeying around.
So, who would you tag as the president on the far right of the monument?