This primary source comes from the Records of the Office of the Chief Signal Officer.
National Archives Identifier:
527532Full Citation: Railroad repair shops; ca. 1860 - 1865; 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/railroad-repair-shops, May 9, 2024]