USNS Mission San Carlos (T-AO-120)

SS Mission San Carlos was a Type T2-SE-A2 tanker built for the United States Maritime Commission during World War II. After the war she was acquired by the United States Navy as USS Mission San Carlos (AO-120). Later the tanker transferred to the Military Sea Transportation Service as USNS Mission San Carlos (T-AO-120). She was a member of the Mission Buenaventura-class oiler and was one of two U.S. Navy vessels named for Mission San Carlos Borroméo de Carmelo, located in Carmel-by-the-Sea, California, the other being USNS Mission Carmel (T-AO-113).

Career
Mission San Carlos was laid down on 1 November 1943 under a Maritime Commission contract by Marinship Corporation, Sausalito, California: launched 12 February 1944; sponsored by Mrs. J. H. Pomeroy; and delivered 15 April 1944. Chartered to Pacific Tankers, Inc. for operations on 15 April, she spent the remainder of the War providing allied forces overseas with the vital fuel needed to keep America's armies on the move (during which time she was awarded the National Defense Service Medal). She was returned to the Maritime Commission on 20 April 1946 and laid up in the Maritime Reserve Fleet at Mobile, Alabama.

Acquired by the Navy on 12 November 1947 and chartered to Marine Transport, Inc. for operations, she was placed in service with the Naval Transportation Service as Mission San Carlos (AO-120). After 1 October 1949 she was under the operational control of the newly created Military Sea Transportation Service as USNS Mission San Carlos (T-AO-120). She remained in service with MSTS until 6 November 1957 when she was transferred to the Maritime Administration (MARAD) for lay up in the Maritime Reserve Fleet at Beaumont, Texas. She was struck from the Naval Vessel Register on the same date.

Sold to Transwestern Associates on 16 May 1966 for conversion to a bulk carrier, she was reacquired by MARAD in the summer of 1966 and resold to Hudson Waterways Corporation for conversion into a combination train ferry and container ship in September, 1966. Renamed Seatrain Maryland, into 1969 she carried cargo between the east and west coasts of the United States and occasionally to Vietnam.

The ship's final disposition is unknown.