The ammunition ship Pyro (AE-1), named for the Greek word meaning fire, was the first U.S. vessel to bear that name. Built at the Navy Yard, Puget Sound, Washington, the Pyro was launched on 16 December 1919 and commissioned on 10 August 1920.
Assigned to the Naval Transportation Service, the Pyro arrived in New York in October 1920 following a month-long trip from Puget Sound. For the next four years, she shipped ammunition, explosives, general cargo, and passengers to ports that included Mare Island, San Francisco, San Pedro, San Diego, Balboa, Guantanamo Bay, Norfolk, Philadelphia, and New York. She traveled as far as the Philippine Islands before her initial decommissioning at Puget Sound on 10 September 1924.
Recalled to duty when war clouds began to form over Europe, the Pyro was recommissioned on 1 July 1939. Again assigned to the Naval Transportation Service. By August 1941, she had made five voyages to the East Coast and five more to Pearl Harbor, Hawaii.