The Algonquin was initially chartered by the United States as a Troop Transport Ship. However, in July 1943 she was acquired by the United States Army for conversion to a Hospital Ship operated by the US Army Transport Service (ATS). The ship was sent to the Alabama Dry Dock and Shipbuilding Company in Mobile, Alabama in July 1943 and the conversion was completed in January 1944.
At the end of January 1944, the US Army Hospital Ship (USAHS) Algonquin, with a full crew of seaman and medical personnel from the 203rd Hospital compliment on board, the ship departed New Orleans, Louisiana for Gibralter. Upon arrival, the ship was cleared to sail to Oran, Bizerte, then finally to Naples, Italy before returning to Charleston, South Carolina on March 28, 1944. Because of problems identified on this first voyage, the Algonquin dropped down to the Merrill Stevens Dry-dock and Repair Company in Jacksonville, Florida for repairs. The ship spent the most part of April 1944 at the shipyard. Once repairs were completed, the ship returned to Charleston, South Carolina, her designated homeport.
In early May 1944, after repairs had been made to the ship in Jacksonville, Florida, the USAHS Algonquin again set sail for Gibralter and Bezerte then returned to Charleston in late May 1944. The Algonquin made a similar trip to Gibralter and Bezerte in June 1944, however, this time she sailed on to Naples before returning to Charleston, SC in late June 1944.
In late July 1944, the Algonquin again sailed to Oran where it would shuttle back and forth to Naples several times. On August 15, 1944, the Algonquin along with eleven other hospital ships, Acadia, Chateau Thierry, John L. Clem, Ernest Hines, Marigold, John J. Meany, St. Mikiel, Seminole, Shamrock, Thistle, and Emily H. M. Weder were involved in the invasion of southern France. It was during this assignment a bomb exploded a few yards away from the Algonquin however, the ship was not damaged.
The Algonquin arrived back in Charleston sometime in mid September 1944. On 22 September 1944 the ship set sail again to Oran and Naples then back to Charleston. Upon her return from Naples and Oran, the Algonquin immediately departed Charleston for Casablanca. Once there she would operate out of the port to Oran, Naples, Leghorn, Tripoli, and Marseille in France. She would not return to Charleston, SC. until February 22, 1945.
On 29 May 1945, the Algonquin departed Charleston and made four more quick trips to Europe and back to Charleston. However, on her last return in September 1945, she began returning to New York, Stapleton Pier 16, Staten Island. From the new homeport in New York, the USAHS Algonquin would make two more trips to Naples, Leghorn, and Marseilles in late 1945.
December 1945 saw the end of service for the Algonquin as a Hospital Ship. When she returned to New York on 14 December 1945, she was dry docked and altered to carry either troops or military dependents.
By early January 1946, the work was completed and the US Army Transport Ship (USAT) Algonquin was back in the Atlantic on 5 January 1946. The USAT Algonquin made two back-to-back trips to Naples to bring Italian war brides to the United States. Many other trips were made during 1946 for the same purpose, including one short voyage to Bermuda.