Mathew B. Brady 1864, June-July U.S. Military Railroads Photographic Headquarters at City Point
Book illustration, photograph with caption Internet - Original source ill-defined Roy and Arthur Meredith, 1979, Mr. Lincoln's Military Railroads: A Pictorial History of the United States Civil War Railroads 1861-1865, (W. W. Norton & Co.), p. 193
With thanks to David Tooley for bringing this to my attention (pers. email, 8 August 2017)