This primary source comes from the Records of the Office of the Chief Signal Officer.
National Archives Identifier:
527823Full Citation: Photograph 111-B-3656; Abraham Lincoln, President, U.S; 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; National Archives at College Park, College Park, MD. [Online Version, https://www.docsteach.org/documents/document/abraham-lincoln, April 19, 2024]