John L. Clem began her service life as the United States Navy troop transport USS Santa Ana (ID-2869). Between the wars she served as a commercial ocean liner under various names. In 1941 she was acquired by the U.S. Army and assigned the name USAT John L. Clem, about which time she was also briefly assigned a US Navy ID, AP-36. She did not serve with the navy however, and spent most of the war as an army transport until being converted into a hospital ship, the USAHS John L. Clem.