This primary source comes from the Records of the Office of the Chief Signal Officer.
Full Citation: 111-SC-8957; Baseball in training camp; 1917; Photographs of American Military Activities, ca. 1918 - ca. 1981; 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/baseball-in-training-camp, May 14, 2024]