Two ships of Moore-McCormack have borne the name Mormactern
SS Mormactern was launched in 1939 as a Type C2 ship under the name Lightning. She was renamed Mormactern in 1940 and acquired by the US Navy in 1941 as a cargo ship and renamed USS Mercury. She was decommissioned in 1946 and transferred to the National Defense Reserve Fleet in 1959. She was scrapped in 1975.
SS Mormactern was launched in 1943 as a Type C1-B ship. She was transferred to the National Defense Reserve Fleet in 1959 and was scuttled in 1968.
