Originally laid down as LST-983 on 22 December 1943 at the Boston Navy Yard; the ship was launched on 10 February 1944, sponsored by Mrs. Neal B. Farwell; and commissioned on 25 March 1944.

The tank landing ship arrived in Derry, Northern Ireland, to discharge fuel oil that had been carried across the Atlantic as ballast and then proceeded to Milford Haven, Wales, and Plymouth, England, where she launched LCT-659.

At 0900 on 5 June, she got underway as flagship of the Vice Commodore, TU GL3, which included 27 American LSTs destined for the British sectors of the Normandy beaches.

On the night of 12 January 1945, submarines attacked her convoy as she was returning from Le Havre with seven other LSTs, but excellent defense by Canadian escorts drove them off.

She arrived in Norfolk, Virginia on 17 July 1945, bringing home 103 men freed from German prisons and PT boat PT-199, which had been secured to her main deck for the crossing.

During Normandy and later in World War II, LST-983 crossed the Channel 102 times, transporting over 10,000 troops and over 3,000 vehicles to beachheads and ports of Europe, and returning more than 2,000 prisoners to England.

During the decade following World War II, LST-983 played a prominent role in the training of Naval, Marine, and Army personnel in the skills needed to maintain a high state of operational readiness.

Middlesex County recommissioned on 27 September 1961 and soon established a pattern of alternating operations between the Virginia Capes area and the Panama Canal Zone training marines and soldiers in the techniques of modern amphibious warfare.

The efficiency of the naval quarantine of Cuba and the mobilization of American armed might quickly persuade the Soviet Union to withdraw its offensive missiles, enabling Middlesex County to return home on 16 December.

The next morning they found the craft adrift, dispersed food and water to 50 prisoners and 5 guards, and took the launch in tow to return her to Isla Cobia that night.

Decommissioned on 15 October 1969, the ship was struck from the Naval Vessel Register on 15 September 1974 and sold for commercial service to L.P. Callimros of Athens, Greece on 12 November 1975.