Zaca was built under a United States Shipping Board contract and completed as SS Zaca in 1918 at Oakland, California, by the Moore Shipbuilding Company. She was acquired by the U.S. Navy for duty with the Naval Overseas Transportation Service (NOTS). Designated Id. No. 3792, she was commissioned as USS Zaca on 30 December 1918 at her builder's yard, Lieutenant Commander James J. Carey, USNRF, in command.