SS Mexican was built in 1907 at San Francisco, California, by the Union Iron Works as a commercial cargo ship for the American-Hawaiian Steamship Company of New York City.

On 23 December 1917, the Department of War transferred Mexican to the U.S. Navy, which gave her the naval registry Identification Number (Id.

Manned by U.S. Navy personnel and operated on a United States Army account, Mexican was assigned to the Naval Overseas Transportation Service and served as an animal transport through the end of World War I. Mexican was in port at St. Nazaire, France on 13 May 1918 when a fire broke out aboard her.

Lookouts aboard the cargo ship USS Alaskan (ID-4542), lying directly astern of Mexican, spotted the fire breaking out.

Alaskan called away her fire and rescue party, which aided Mexican's men in controlling the blaze before it did serious damage.