She was built in 1943 for the United States Maritime Commission as SS Marine Eagle, a Type C4-S-B1 tank carrier, by Sun Shipbuilding during World War II.

Marine Eagle (MC hull 735) was laid down by the Sun Shipbuilding and Dry Dock Company of Chester, Pennsylvania under a United States Maritime Commission contract on 5 December 1942 and launched 10 May 1943 sponsored by Mrs. R. M.

In May, she steamed to Portland, Oregon, for inactivation overhaul, after which she was laid up in the National Defense Reserve Fleet (NDRF) at Olympia, Washington, on 29 October.

Originally assigned to Military Sea Transport Service, Atlantic, she was converted for heavy lift in 1953–54 by the Bethlehem Steel Company of Brooklyn, New York.

Private Leonard C. Brostrom continued heavy lift operations through the 1960s and 1970s, carrying such diverse cargoes as chemical weapons to Okinawa for Project Red Hat in 1963 through 1964, a 101-long-ton (103 t) turbo-electric power plant, several 85-long-ton (86 t) diesel-electric locomotives (85 t.