Pelias was laid down as SS Mormacyork under Maritime Commission contract by Sun Shipbuilding and Dry Dock Co., Chester, Pennsylvania, 8 May 1939; launched 14 November 1939; sponsored by Miss Barbara W. Vickery; and delivered to Moore-McCormick Steamship Co., 1 April 1940.

Steaming via San Diego, California, she arrived Pearl Harbor 21 November 1941 as the tender for Submarine Squadron Six.

During the sneak attack her guns splashed one enemy torpedo plane, and damaged a second, as they made their deadly runs along the main channel little more than 100 yards from her port side.

After servicing almost a score of submarines at Pearl Harbor, Pelias steamed to San Francisco late in May 1942 and took on spare parts, provisions, and ammunition.

Based at San Diego when hostilities ended 15 August, Pelias steamed to Tiburon Bay 10 September 1945, thence to Mare Island 24 February 1946.