[2] The ship was laid down on 14 February 1942 by United Engineering Co. of San Francisco, California, at Mare Island Navy Yard.

She was an element of the support unit for the ships engaged in the Battle for Leyte Gulf in late October 1944 and for the 3rd Fleet during the major portion of the following month.

On the afternoon of 14 May 1945, while on station in the waters between Okinawa and the Western Carolines, Sioux took her place beside her big sisters in the battle fleet when her gunners spotted a Kaiten, a Japanese two-man, suicide submarine, and sank it with 40 millimeter gunfire.

From January until September 1946, the tug was in the Marshall Islands supporting "Operation Crossroads", the atomic bomb tests conducted at Bikini Atoll.

On 2 December 1946, Sioux began inactivation procedure at Terminal Island Naval Shipyard, Long Beach, California.

Two months after her return to San Diego, she underwent a three-month overhaul; then resumed towing duties along the west coast.

Sioux returned to operations out of Subic Bay until 10 September when she commenced another 18 days of surveillance in the South China Sea.

During each of her Far East tours, she entered the war zone around Vietnam, visiting Da Nang several times, Cam Ranh Bay at least once and other, less well known places such as Qui Nhơn and Vũng Tàu.