[2] At this time the United States Army was small and generally assigned to defend the nation's frontiers from attacks by Indians.

The steamer CSS Fanny was armed as a gunboat and operated by the Quartermaster Department of the Union Army during the American Civil War.

[5] At the close of the war, the fleet of 590 ocean transports in service on July 1, 1865, was reduced to 53 vessels by June 30, 1866.

[7] Army Colonel Frank J. Hecker approached the Atlantic Transport Line to charter its fleet, and was refused.

He then offered to buy the vessels he sought and a deal was struck, subject to the approval of the Secretary of War Russel Alger.

The Atlantic Transport Line sold Manitoba, Massachusetts, Mohawk, Mobile, Michigan, Mississippi, and Minnewaska.

[9] These and other ships acquired during the Spanish-American War were the core of the Army Transport Service's ocean-going fleet until World War I. ATS operated the Army's large ships but did not operate smaller vessels of the harbor boat service (tugs, launches, small and short range supply boats), the mine planters of the Coast Artillery Corps or any vessels of the Corps of Engineers.

[13] The USAT Admiral H. T. Mayo served as an Army transport at the end of World War II.

Naval personnel, either Armed Guard or communications were under their own commander independent of ship's master or Corps representatives in tactical matters.

[21] Six Liberty ships were converted at Point Clear, Alabama into floating aircraft repair depots, operated by the ATS, starting in April 1944, to provide mobile depot support for B-29 Superfortress and P-51 Mustangs based on Guam, Iwo Jima, and Okinawa beginning in December 1944.

They were also fitted with landing platforms to accommodate four R-4 helicopters, creating the first seagoing helicopter-equipped ships, and provided medical evacuation of combat casualties in both the Philippines and Okinawa.