Alexander Gardner, Allan Pinkerton, President Abraham Lincoln and Major General John A. McClernand in Antietam, Maryland, 1862, photograph, Washington, D.C., Library of Congress, 1977. No. 0147, Public Domain via Wikimedia Commons.
Alexander Gardner, Allan Pinkerton, President Abraham Lincoln and Major General John A. McClernand in Antietam, Maryland, 1862, photograph, Washington, D.C., Library of Congress, 1977. No. 0147, Public Domain via Wikimedia Commons.