The Union Signaling station was located on the roof of the Cheves' Rice Mill across the river from Fort McAllister.

Major General Sherman and Brigadier General Howard are shown studying a map in final preparations for the land attack on Fort McAllister, the last major battle of the Atlanta Campaign.
Sherman has directed that Captain McClintock, his Signal Officer, order General Hazen to commence the land assault on the Confederate Fort. On the Signaling platform is Corporal Magner with his wig wag flag.