[President Abraham Lincoln, Major General John A. McClernand and E. J. Allen (Allan Pinkerton)], 1862, by Alexander Gardner (American, Glasgow, Scotland 1821–1882 Washington, D.C.)

[President Abraham Lincoln, Major General John A. McClernand (right), and E. J. Allen (Allan Pinkerton, left), Chief of the Secret Service of the United States, at Secret Service Department, Headquarters Army of the Potomac, near Antietam, Maryland], October 4, 1862
Alexander Gardner (American, Glasgow, Scotland 1821–1882 Washington, D.C.)
Albumen silver print from glass negative
The Metropolitan Museum of Art, Gilman Collection, Gift of The Howard Gilman Foundation, 2005 (2005.100.1221)
Image: © The Metropolitan Museum of Art, New York.