The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 8: Soldier Life and Secret Service.
Francis Trevelyan Miller, Ed.

Headquarters of the Union signal corps at Vicksburg 1864

After the surrender of Vicksburg, July 4, 1863, the Signal Corps of Grant's army was under the command of Lieutenant John W. Deford, a recently exchanged prisoner of war. Its ___location was on the southern continuation of Cherry Street near the A. & V. railway. From the balcony of the house are hanging two red flags with square white centers, indicating the headquarters of the Signal Corps. Many times before the fall were orders flashed by night by means of waving torches to commands widely separated; and in the daytime the signal-men standing drew on themselves the attention of the Confederate sharpshooters. A message begun by one signal-man was often finished by another who picked up the flag his fallen companion had dropped. The tower at Jacksonville, Florida, over a hundred feet high, kept in communication with the signal tower it Yellow Bluff, at the mouth of the St. John's River. Note the two men with the Signal Corps flag on its summit. Just below them is an enclosure to which they could retire when the efforts of the Confederate sharpshooters became too threatening.

Signal stations from the Mississippi to the Atlantic: evidence of the Signal-man's activity throughout the theater of war.

After Grant arrived and occupied Chattanooga, Bragg retired up the Cumberland Mountains and took up two strong positions—one upon the top of Lookout Mountain, overlooking Chattanooga from the south, and the other on Missionary Ridge, a somewhat lower elevation to the east. His object was to hold the passes of the mountain against any advance upon his base at Dalton, Georgia, at which point supplies arrived from Atlanta. Grant, about the middle of November, 1863, advanced with 80,000 men for the purpose of dislodging the Confederates from these positions. At the very summit of Lookout Mountain, ‘The Hawk's Nest’ of the Cherokees, the Confederates had established a signal station from which every movement of the Federal Army was flashed to the Confederate headquarters on Missionary Ridge. The Federals had possessed themselves of this signal code, and could read all of Bragg's messages. Hence an attempt to surprise Hooker when he advanced, on November 23d, failed.

Tower at Jacksonville

Lookout Mountain—the anticipated signals