The steel-hulled, single-screw cargo vessel was laid down as SS Excelsior under a Maritime Commission contract (MC hull 589) on 23 July 1942 at Sparrow's Point, Maryland, by the Bethlehem Sparrow's Point Shipyard; renamed Windsor and classified a transport, AP-100, on 5 October 1942; launched on 28 December 1942; sponsored by Miss Patricia Moreell, the daughter of Rear Admiral Ben Moreell, Chief of the Bureau of Yards and Docks; reclassified an attack transport, APA-55, on 16 June 1943; and commissioned at the Norfolk Navy Yard, Portsmouth, Virginia, on 17 June 1943.

However, the following evening, a Japanese air raid blew up a captured ammunition dump and ensuing fires destroyed nearly 60 percent of the supplies landed.

Simultaneous with the landings at Tanahmerah and Humboldt Bays, the 7th Amphibious Force also put troops ashore to secure Aitape and its vital airstrip.

Three days before the assault troops were slated to go ashore, ships and planes hurled an intensive air and surface bombardment against the Japanese defenses, while minesweepers cleared the waters off Peleliu and Angaur Islands, and underwater demolition teams destroyed beach obstructions.

Windsor emerged unscathed and put into San Pedro Bay on the morning of 14 November, commencing her unloading at 0804 and completing it at 1315, having disembarked the troops and equipment of the 32d Division.

The attack transport lay off Samar for nearly two weeks before she received onward routing to return to San Francisco and, on her ensuing voyage, touched at Peleliu, Guam, Saipan, Tinian, and Pearl Harbor to pick up passengers.

Shifting to Honolulu, Windsor there picked up troops slated for transportation to Okinawa and, as part of Task Unit (TU) 96.6.15, proceeded to Hagushi Beach, where she remained from 25 July to 5 August.

While Windsor lay at anchor at Ulithi lagoon, Japan accepted the unconditional surrender terms of the Potsdam Declaration; and hostilities ceased on 14 August.

After embarking troops of the American Division and supplies on 31 August, Windsor sailed for Japan as part of the Tokyo occupation force.

The attack transport returned to Cebu, loaded equipment, and embarked the troops of the Army's 77th Division, and landed that unit at Hakodate, Hokkaidō, in early October.

After the occupation of Japan, Windsor served under the aegis of Commander, Service Force, Pacific, reporting for duty with Operation Magic Carpet on 19 November.

Decommissioned on 4 March 1946, Windsor was struck from the Navy list on 12 April 1946 and delivered to the War Shipping Administration, at Mobile, Alabama, on 1 August 1946, for disposition.