Sheridan, APA-51, was an Ormsby-class attack transport named for five counties named for General Philip H. Sheridan. Moore Dry Dock at Oakland laid her down on 5 August 1942 as the merchant ship Messenger, a C2 hull, Maritime Commission hull 290. She was assigned to the Navy on 5 October 1942 as the transport Sheridan (AP-96) and reclassified APA-51 on 1 February 1943. Wikipedia gives her launch as 11 November 1942, and NavSource gives 10 October 1942. She was acquired and commissioned on 31 July 1943, Commander John J. Mockrish, USNR, in command.
She loaded Marines at Wellington and landed them at Tarawa on 20 November 1943. After exercises on the California coast she sailed from San Diego on 13 January 1944 and arrived off Kwajalein on 31 January. Her troops landed at Roi on 1 February while she stayed off the beaches offloading cargo and acting as a temporary hospital ship until the hospital ship Solace arrived. She sailed on 8 February.
She arrived at Saipan on 15 June 1944, debarked troops, and embarked a large group of casualties on 18 June. NavSource lists two men killed and six wounded at Saipan, buried at sea on 18 June. She debarked troops at Guam on 23 July, landed troops in the first waves at Leyte on 20 October, and landed troops at Lingayen Gulf on 9 January 1945, afterward taking on 108 Navy casualties and survivors, mainly from the escort carrier Ommaney Bay. She put troops ashore at Okinawa on 1 April 1945. She entered Tokyo Bay as the surrender was being signed on 2 September and offloaded troops on 3 September.
She was decommissioned at Mobile on 5 March 1946, returned to the Maritime Commission on 7 April, and struck on 12 April 1946. She was sold to United States Lines in 1947, renamed Pioneer Sun and later American Scientist, damaged by an explosion, and scrapped in 1969. She earned seven battle stars.