SS Los Angeles was built by Union Iron Works at San Francisco, California, as a commercial tanker in 1916 for the Union Oil Company of California. The U.S. Navy acquired her from Union Oil in 1917 for World War I service under a bareboat charter, gave her the naval registry Identification Number (Id. No.) 1470, and commissioned her as USS Los Angeles on 9 August 1917 at New Orleans, Louisiana, with Lieutenant Commander Alexander Mackenzie in command. During the remainder of 1917, Los Angeles operated along the United States East Coast and United States Gulf Coast and made two cruises with the Atlantic Train Force.