The original four operators of the United States Military Telegraph Corps The figure standing is Samuel M. Brown. Those in the front row, reading from left to right, are David Strouse, David Homer Bates and Richard O'Brien.

Title from published copy of photograph found with ambrotype.
Case: leather, geometric design.
Note inside case: Harrisburg, April 27th, 1861.
Forms part of: Ambrotype/Tintype photograph filing series (Library of Congress).
Exhibited: "The Civil War in America" at the Library of Congress, Washington, D.C., 2012-2013.