1950-1959

1944-1949

1960-1989

After the outbreak of war in Korea, San Marcos was ordered activated. Recommissioned on 26 January 1951, she completed shakedown in March, was assigned to the Atlantic Fleet's Amphibious Force, and, in May, sailed for the Panama Canal and Little Creek, Virginia.

She arrived at the latter in late May and, soon thereafter, commenced arctic summer resupply operations, under the Military Sea Transportation Service (MSTS), to bases in Canada andGreenland. With the fall, she moved to the Caribbean Sea for fleet exercises, then returned home. In November, she shifted to Baltimore, Maryland, for a shipyard overhaul, and with the new year, 1952, resumed active duty.

Caribbean exercises took her into March. In April she departed Norfolk, Virginia, embarkedMarines and their equipment at Morehead City, and headed east for her first Mediterraneandeployment. She transited the Straits of Gibraltar in early May and operated with the Sixth Fleet, ranging from the south of France to Benghazi and Phaleron Bay, into October. She then recrossed the Atlantic, and, after disembarking the Marines in North Carolina, proceeded to Little Creek. She resumed east coast operations with a joint Army–Navy exercise in November.

During 1953, San Marcos conducted exercises and carried cargo along the east coast and in the Caribbean and underwent overhaul at Boston, Massachusetts. Winter, spring, and fall of 1954 saw a continuation of those operations including a reserve training cruise, while the summer brought a return to arctic waters for resupply missions. In January 1955, she proceeded again to the Mediterranean Sea.

Completing that deployment in May, she resumed a schedule of east coast, Caribbean, and – during the summers of 1956 and 1957 – polar logistic support operations. In September 1958, she was again deployed to the Mediterranean for a six-month tour with the Sixth Fleet. She rejoined theSecond Fleet in March 1959; and, in May, tested recovery methods for Project Mercury. During the summer, she participated in Operation Inland Seas, conducted in the Great Lakes and made possible by the opening of the St. Lawrence Seaway. Amphibious force exercises and local operations occupied the remainder of the year.