On 31 July 1942, the Department of War recognized the need for a single manager of Army transportation and created a new branch, the Transportation Corps. Since the Revolutionary War, Army transportation had evolved through two branches, the Quartermaster Corps and the Corps of Engineers. The demands of World War I made the Army first realize its need for a single manager for military transportation. So began an evolution over the next quarter century that culminated in the birth of the Transportation Corps during the opening months of World War II.
Transportation as a function has existed from the beginning of American military history. The Quartermaster Department was long responsible for wagon and boat transportation, except for harborcraft; responsibility for harborcraft resided with the Corps of Engineers since it had the mission of maintaining ports. When the Army adopted the use of military railroads during the Civil War, that function also fell to the Corps of Engineers since it was responsible for repairing tracks and building bridges.
During the 19th century, the Army was too small to require much specialization. So transportation requirements during peacetime could be managed by the Quartermaster Department. During war, however, the need for military transportation habitually expanded into organizations that managed the different modes, such as wagons, boats, and railroads. [The Quartermaster, Subsistence, and Pay Departments were consolidated in 1912 to create the Quartermaster Corps.]