LST-603 was laid down on 5 November 1943 at Seneca, III., by the Chicago Bridge & Iron Co.; launched on 14 March 1944; sponsored by Mrs. Etla N. Hobart; and commissioned on 5 April 1944, Ens. William B. Sweet in command.
During World War II, LST-603 was assigned to the European theater and participated in the invasion of southern France in August and September 1944. Following the war, she performed duties with the Amphibious Force, U.S. Atlantic Fleet, including one deployment to the Mediterranean in 1950. The ship was decommissioned on 12 May 1955. On 1 July that same year, she was redesignated Coconino County (LST-603) after a county in Arizona. She was recommissioned on 8 June 1966 and operated in the Vietnam theater commencing in 1966 until she was transferred to the Republic of Vietnam Navy on 4 April 1969 where she served as Vung Tau (HQ-503).
LST-603 received one battle star for World War II service, and six battle stars and two awards of the Meritorious Unit Commendation for Vietnam service.