The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 5: Forts and Artillery.
Francis Trevelyan Miller, Ed.

[302] 473 miles of road from Louisville, through Nashville and Chattanooga, to Atlanta, 288 miles of which were constantly subject to raids from the foe — the portion from Nashville to Atlanta; that this single-stem road supplied one hundred thousand men and thirty-five thousand animals for one hundred and ninety-six days; and that to have delivered as much food by wagon would have been entirely impossible, since even to have hauled as much a short distance would have taken thirty-six thousand eight hundred six-mule wagons, and, when the state of the roads was considered, an attempt to supply by these means would have been an absurdity. Whereupon he reiterated that the Atlanta campaign would have been an impossibility without the railroads.

When Sherman evacuated Atlanta, preparatory to his march to the sea, he destroyed the railroad in his rear, blew up the railroad buildings in the city, sent back his surplus stores and all the railroad machinery that had been accumulated by his army, and, as far as possible, left the country barren to the Confederates. The stores and railroad stock were safely withdrawn to Nashville, and after the dispersion of Hood's army the construction corps again took the field, reconstructed the road to Chattanooga, then to Atlanta, and later extended it to Decatur, Macon, and Augusta.

At one time, just prior to the close of the war, there were 1,769 miles of military railroads under the direction of General McCallum, general manager of the military railroads of the United States. These roads required about three hundred and sixty-five engines and forty-two hundred cars. In April, 1865, over twenty-three thousand five hundred men were employed. The results of the work of the corps were recognized throughout the world as remarkable triumphs of military and engineering skill, highly creditable to the officers and men.