Southport, a 245 gross ton coastal passenger steamship, was built at Boston, Massachusetts in 1911 and operated in New England waters for the next several years. Chartered by the Navy in mid-November 1918, she was placed in commission as USS Southport (without the "ID" series number typically given to vessels acquired by the Navy during the World War I era). She served the First Naval District, in the Boston area, as an ambulance boat until November 1919 and was then returned to her owners.