The aftermath of the war had Mooremack owning 41 ships and, in 1946, 76 chartered ships from the US Maritime Commission. In 1949, Mooremack repaid a government loan subsidizing the South American services, and repaid its mortgages, thus essentially owning its fleet. Mooremack was involved in the
Korean War. Notably, its cargo ship rescued some 14,000 refugees from
Hungnam in December 1950. In 1954, Mooremack withdrew the liner
Uruguay from its New York – River Plate route, leaving
Brazil and
Argentina to continue a reduced service.
Uruguay was laid up in the
National Defense Reserve Fleet in the
James River, Virginia. In 1958, Mooremack introduced a new and to the route, while the old
Brazil and
Argentina joined
Uruguay in the Reserve Fleet on the James River. The new pair of liners worked the route until 1969, when declining passenger numbers made them unprofitable and Mooremack laid them up. In 1964–1965, Mooremack placed its Constellation-class freight liners in service,
Mormacargo,
Mormaclynx,
Mormacvega,
Mormacdraco,
Mormacaltair and
Mormacrigel. The fast, state of the art vessels completed Mooremack's modernization program begun in 1956. On 11 February 1966,
Mormacaltair set sail from New York for Europe, establishing the first regularly scheduled transatlantic container service. Within weeks, Mooremack was joined by
United States Lines and
Sea-Land Service, but Mooremack failed to exploit its first-off-the-mark lead and make the investment in fully cellular
container ships necessary to realize the maximum efficiencies and cost savings that containerization promised. Left behind by U.S., British and European ship lines and container line consortia, Mooremack abandoned the North Atlantic trade in 1970 to concentrate on its cargo routes to South America and Africa, and sold four brand new combination break-bulk, container, roll-on/roll-off ships to
American Export-Isbrandtsen Lines to offset losses. The idled 1958 liners
Argentina and
Brasil were sold to
Holland America Line in 1972. Mooremack had two of its newest freight liners,
Mormacaltair and
Mormadraco of 1965, lengthened and converted into partial cellular container ships in 1975–1976. The four other "Connies" of 1964–1965 were similarly converted in 1982. Diversification into the natural resources and energy fields proved not to be as profitable as the company had hoped, and the energy crisis of the late 1970s and business recession of the early 1980s made operating costs unsustainable.
Malcom McLean's United States Lines bought out Moore-McCormack in December 1982, and its remaining ships were absorbed into the US Lines fleet and later sold off or turned over to the
Maritime Administration (MARAD). (Subsequently,
Mormacaltair in 1990 was converted into a crane ship, USS
Green Mountain State (T-ACS-9) for MSC, and in 1991
Mormacdraco also into USS
Beaver State (T-ACS-10).
Mormacdraco/
Beaver State then underwent a further conversion in 2009 into USS
Pacific Tracker (XTR-1) for the Missile Defense Agency. The ex-States Steamship acquired ship,
Mormactide, was converted in 1988 into the school ship,
TS Empire State VI (TAP 1001) for the New York State Maritime College. ==Operating companies==