Mediterranean, 1942–1944

After shakedown training in the Chesapeake Bay, during which she also served as training ship for crews to be assigned to other tank landing ships, LST-389 departed Norfolk, Virginia on 19 February 1943, bound for Bayonne, New Jersey where she took on board one tank landing craft (LCT), United States Army troops, and a cargo of medical supplies. Sailing with convoy UGS 6A on 19 March, she proceeded via Bermuda to North Africa and reached Nemours, Algeria on 13 April. Soon shifting to the Arzew Naval Base, Algeria the ship became the flagship for Captain Frank Adams, Commander, LST Group 5, Flotilla 2. LST-389 was soon involved in the campaign to invade Sicily, a steppingstone to Italy.

Invasion of France, 1944–1945

Clearing Oran on 12 November LST-389 sailed for England in MKS-30, a convoy which endured a glider-bomb attack, launched by German Dornier bombers, without suffering any losses. Shortly before Thanksgiving the ship, now a veteran of two major amphibious landings, arrived at Plymouth and waited for orders. Following a period in drydock there for minor repairs beginning on 13 December, LST-389 departed Plymouth on 20 December and reached Falmouth the same day. On Christmas Eve, she started preparing for the invasion of France.

"With the beginning of 1944..." wrote the ship's historian, "...the ship moved from place to place, beaching, retracting, learning the new methods of war." Finally ending up in the Welsh port of Milford Haven, LST-389 stayed there for the rest of January and all of February before shifting to Swansea, Wales for more training. After operating there until 27 April, LST-389 proceeded to Lisahally on the shore of Lough Foyle in Northern Ireland to receive six 40-millimeter and six 20-millimeter guns. Following more repairs and alterations at Milford Haven, LST-389 spent the rest of May training for the assault on Hitler's "Atlantic Wall." Loading Army vehicles and embarking troops at Falmouth on 2 June 1944 she got underway on 4 June and proceeded to the task force anchorage where the ship lay until setting out for France on the following morning. After anchoring in Baie de la Seine at 0927 on 7 June, she began resupply operations for the Normandy beachhead that afternoon. One of her LCVP coxswains suffered wounds at 1645 when his craft was hit on its way to the beach. The next morning, German planes braved heavy antiaircraft fire to attack the shipping off the invasion beaches. Four bombs landed in the sea near LST-389 causing "minor hull vibrations." The tank landing ship unloaded her embarked vehicles that afternoon, 8 June, and survived another nocturnal bombing attack at 0034 on the 9th before getting underway for Southampton later that morning.

For the rest of June, LST-389 shuttled supplies and men between Southampton and various beaches along the northern coast of France. Her cargoes included food, medical supplies, and vehicles. After the port's capture by the Allies in July, she added Cherbourg to her itinerary and, railroad tracks having been installed in her tank deck, began carrying rolling stock in early September. In the course of these train-ferrying operations, LST-389 struck an underwater obstruction at Grand Rade, Cherbourg, on 12 November. Major leaks in her main engine room resulted. Unable to make any headway against the rising water, the tank landing ship, aided by two tugboats, was beached. Seven hours of shoring, patching, and pumping freed the engine room of unwanted water. With the aid of British tugs, LST-389 then completed her ferry mission before LST-355 towed her back to Devonport, England. Following major repairs in drydock, the ship received an overhaul alongside Atlas before resuming active service in mid-January 1945. She again shuttled railroad cars and passengers between England and France. While returning from Le Havre to Portland, Dorset, early on the fog-shrouded morning of 5 February, LST-389 was rammed by the civilian merchantman SS Chapel Hill Victory. The collision ripped a hole 18 feet (5.5 m) wide in the tank landing ship from main deck to bottom and killed one member of her crew. LST-389 then proceeded to Portland under her own power. After a week at anchor off Portland, LST-389 put into Plymouth for another drydocking which lasted into late March. LST-389 next made one trip carrying vehicles to Cherbourg and two more to Le Havre before she had LCT skids installed on her main deck at Falmouth.

Return to the US, 1945

Picking up LCT-814 and a "general cargo" at Plymouth, LST-389 put into Belfast, Northern Ireland on 8 May, the day after Germany surrendered. On the 11th, she sailed in a convoy bound for the United States and reached Norfolk on the last day of the month. Following overhaul at New York, the ship proceeded to Little Creek, Virginia on 5 September 1945. Since the war in the Pacific had ceased in mid-August, LST-389's orders to proceed to that area of the world were cancelled. Instead, she returned to New York to pick up another LCT and then sailed for Jacksonville, Florida.

Decommissioning and transfer, 1945–1960

She arrived at the Inactive Fleet Berthing Area at Green Cove Springs, Florida on 9 October 1945 and reported for duty with the Inactive Fleet. Decommissioned on 12 March 1946 she was placed in reserve on 1 July 1946. LST-389 remained in reserve, first at Green Cove Springs and later at Charleston, Mayport, and again in Green Cove Springs, through the 1950s. While inactive, she was named USS Boone County (LST-389) on 1 July 1955. Her name was struck from the Naval Vessel Register on 1 June 1959.

LST-389 received three battle stars for her World War II service.