Windsor, APA-55, was the lead ship of her class of attack transports. Bethlehem Steel at Sparrows Point laid her down on 23 July 1942 as the merchant ship Excelsior, Maritime Commission hull 589. She was renamed Windsor and classified AP-100 on 5 October 1942, and was launched on 28 December 1942 (NavSource gives 29 December), Miss Patricia Moreell sponsoring. She was reclassified APA-55 and commissioned at Norfolk on 17 June 1943, Commander Douglas C. Woodward in command.
After training in the Chesapeake she left the east coast on 9 December 1943 and joined Transport Division 4 at Pearl Harbor. She embarked the 3rd Battalion, 17th Regiment, 7th Infantry Division, and sailed on 22 January 1944 with Task Force 52 for the Marshalls. She took part in the Kwajalein assault and, after the atoll was secured early in February, went to the Ellice Islands. She was diverted to Humboldt Bay after the Hollandia ammunition dump explosion, landing troops of the 34th Infantry Division there on 24 April and 32nd Division units at Aitape on 3 May.
She landed the 2nd Battalion, 3rd Marines, at Guam on 21 July 1944, put ashore 1st Marine Division elements at Peleliu on 15 September, and reached Leyte on 22 October, finishing her unloading in record time. On 14 November 1944 she unloaded 32nd Division troops in about five hours despite air attacks, averaging 95.9 tons an hour.
She was overhauled at Oakland from 13 December 1944 to 16 February 1945 and carried Seabees to Samar. She was decommissioned on 4 March 1946, struck on 12 April 1946, and transferred to the War Shipping Administration on 1 August 1946. She was sold in 1947 and scrapped at Kaohsiung, Taiwan, in 1972; NavSource gives the scrapping sale as 9 May 1972. She earned six battle stars.