Sumter was the third of the Newport class which were designed to meet the goal put forward by the United States amphibious forces to have a tank landing ship (LST) capable of over 20 knots (37 km/h; 23 mph).

This made the Newport class the first to depart from the standard LST design that had been developed in early World War II.

The LST carried 1,750 long tons (1,780 t) of diesel fuel for a range of 2,500 nautical miles (4,600 km; 2,900 mi) at the cruising speed of 14 knots (26 km/h; 16 mph).

The ship was also equipped with a bow thruster to allow for better maneuvering near causeways and to hold position while offshore during the unloading of amphibious vehicles.

[3][5] The Newport class were larger and faster than previous LSTs and were able to transport tanks, heavy vehicles and engineer groups and supplies that were too large for helicopters or smaller landing craft to carry.

[1][2] The Newport class has the capacity for 500 long tons (510 t) of vehicles, 19,000 sq ft (1,800 m2) of cargo area and could carry up to 431 troops.

[1][7] The vessels also have davits for four vehicle and personnel landing craft (LCVPs) and could carry four pontoon causeway sections along the sides of the hull.

[6][9] Named for the county in South Carolina, Sumter was launched on 13 December 1969, sponsored by the wife of United States Senator Strom Thurmond.

On 29 August, Sumter sailed to Morehead City, North Carolina, where the LST embarked Marines, and then steamed to join the 6th Fleet in the Mediterranean Sea.

Sumter called at ports in Spain, Turkey, Sardinia, Sicily, Italy, Crete, and Greece before returning to Little Creek on 10 December 1973.

On 12 February 1974, Sumter sailed to Morehead City to embark Marines for exercises in the Caribbean Sea and returned to Little Creek on 8 March.

In April the LST made a voyage to Boston and, the following month, held additional exercises in the Caribbean before returning to her homeport on 3 July.

[10] 17 August 1986 Sumter sortied to embark Marines at Morehead City to begin the first phase of Deployment Northern Wedding 1986.