This primary source comes from the Records of the Office of the Chief Signal Officer.
National Archives Identifier:
530480Full Citation: US Military Telegraph Operators, Headquarters, Army of the Potomac. July 1863.; 7/1863; Mathew Brady Photographs of Civil War-Era Personalities and Scenes, 1921 - 1940; Records of the Office of the Chief Signal Officer, Record Group 111. [Online Version, https://docsteach.org/documents/document/us-military-telegraph-operators-headquarters-army-of-the-potomac-july-1863, March 17, 2025]