The above photo was taken on October 3rd, 1862 at Antietam, Maryland following the battle of Antietam.
You may be able to spot Lincoln, but how about McClellan?
Can you find Custer?
Hint: Some may claim him as the inventor of the photobomb.
Answer: Yes, that's him at the far right end of the line.
At the time of the photo, Custer was a captain in the Army and aide-de-camp to McClellan.
He appears to be holding a blade, but doesn't seem to be using it to shave.
(Clicking on the photo will show the image in full along with caption).