Maintenance of road and structures for each line (as distinct from the reconstruction work left to the Construction Department) was in charge of a Superintendent of Repairs, assisted by such supervisors, road-masters and foremen as he needed to control and direct his working staff; and maintenance of rolling stock was delegated to (1) a Master Machinist, responsible for repairs to locomotives, and (2) a Master of Car Repairs.
These various officers were independent of each other, and all of them reported direct to the General Superintendent. The maximum force employed at any one time in the Transportation Department of the Military Division of the Mississippi (as distinct from the military lines in Virginia and elsewhere) was about 12,000 men.
A sufficient staff of competent railwaymen for the operation of the Military Railways was difficult to get, partly because of the inadequate supply of such men in the United States at that period, and partly because those still at work on railways not taken over for military purposes were unwilling to give up what they found to be exceptionally good posts; but of the men whose services he was able to secure McCallum speaks in terms of the highest commendation.
Having got his Department and Construction Corps into working order, McCallum had next to turn his attention to ensuring an adequate supply of locomotives and cars, with the necessary shops, tools and materials for keeping them in working order. Here the Secretary of War again came to his help, issuing, on March 23, 1864, an Order addressed to locomotive manufacturers in which he stated that Colonel McCallum had been authorised by the War Department to procure locomotives without delay for the railways under his charge, and proceeded:—
In order to meet the wants of the Military Department of the Government, you will deliver to his order such engines as he may direct, whether building under orders for other parties or otherwise, the Government being accountable to you for the same. The urgent necessity of the Government for the immediate supply of our armies operating in Tennessee renders the engines indispensable for the equipment of the lines of communication, and it is hoped that this necessity will be recognised by you as a military necessity, paramount to all other considerations.—By order of the President.
In January, 1864, McCallum had estimated that he would require 200 locomotives and 3,000 cars for the lines to be operated from Nashville, and towards this number he then had only 47 locomotives and 437 cars available. There was thus a substantial shortage which had to be made good; but the manufacturers, inspired by "a spirit of zealous patriotism," responded heartily to the appeal made to them, putting their full force on to the completion of further supplies. These were furnished with a speed that surpassed all previous records.
Then, to maintain the locomotives and cars in good condition—more especially in view of the constant attempts made by the enemy to destroy them—extensive machine and car shops were built at Nashville and Chattanooga. Those at Nashville—the terminal station for 500 miles of railway running south, east or west—had, at times, as many as 100 engines and 1,000 cars awaiting repair.
Next to that insufficiency of engines and rolling stock which hampered the movements of both combatants came the difficulty in the way of obtaining further supplies of rails, whether for new lines or to take the place of those which had either worn out or been so bent and twisted by the enemy that they could not be used again without re-rolling. For the Confederates, cut off by the advance of General Grant to the south and west from their sources of supply, the want of iron for new rails was declared to be a worse evil than was the lack of gold for the Federals.
One expedient resorted to by the Federal Government, on finding they could not procure from the manufacturers all the rails they wanted, was to pull up the railway lines that were not wanted for military purposes and use their rails for relaying those that were. Altogether the rails on over 156 miles of track in Virginia and the Military Division of the Mississippi were thus taken up and utilised elsewhere. Later on the Federal Construction Corps erected at Chattanooga some "very superior" rolling mills, equipped with all the latest improvements in the way of machinery and mechanical appliances; though these mills did not actually get to work until April 1, 1865. Their production of new rails during the course of six months from that date was 3,818 tons, this supply being in addition to nearly 22,000 tons which the Federal Government obtained by purchase.