DuPage was named for DuPage County, Illinois and was launched on 19 December 1942 as Sea Hound (AP-86) by Ingalls Shipbuilding Co., Pascagoula, Mississippi, under a Maritime Commission contract; sponsored by Mrs. Leigh R. Sanford; reclassified APA-41 on 1 February 1943; placed in ferry commission on 28 February 1943, decommissioned on 17 March 1943 for conversion by Todd-Erie Basin Dry Docks, Brooklyn, N.Y.; and recommissioned on 1 September 1943.

DuPage reached San Diego, California, from Norfolk, Virginia on 2 November 1943 to serve as flagship for a transport division during training.

After evacuating casualties to Eniwetok, and exercising off Espiritu Santo, DuPage returned to Guadalcanal on 27 August to replenish, overhaul her landing craft, and train for the invasion of the Palau Islands.

Despite her injuries DuPage continued to fulfill her duty as guide ship and arrived safely at Leyte three days later to transfer her casualties and undergo emergency repairs.

After minor alterations she was designated as flagship for Transport Division 63 and sailed on 12 August with U.S. Army Air Force personnel whom she disembarked at San Pedro Bay, Leyte on 5 September.

Three days later she was assigned to "Magic Carpet" duty and made two voyages between Guam and the west coast to return veterans until 5 January 1946 when she arrived at Portland, Oregon.