4 1/2 x 3 in. albumen photograph on 6 x 4 1/2 in. mount (even toning to print; mounting traces on verso, not affecting applied paper label). Mount recto with Gardner & Gibson's copyright in lower margin. Verso with applied paper label including series title, "Brady's Album Gallery, No. 577," and image title. 

This famous image was taken by Alexander Gardner on the Antietam Battlefield two days after the bloodiest battle in American history. Knap’s Battery "E" was commanded by Captain Joseph M. Knap and served with distinction at Antietam and Gettysburg. There are two monuments to this battery at Gettysburg including one at the top of Culp’s Hill. This was one of the “Independent” Pennsylvania batteries assigned to Geary’s Division, 20th Army Corps. General Geary’s son, a lieutenant, was killed while serving in this battery. See National Park Service Antietam Battlefield website, Historic Photographs by Alexander Gardner just after the Battle, and Library of Congress image #LC-B811-577. A detailed discussion of this photo appears in William Frassanito’s “Antietam.”