Pan-Atlantic

Malcolm McLean acquired the Pan-Atlantic Steamship Corporation in January 1955 from Waterman Steamship for $7 million with seven C-2 cargo ships included in the sale. 

McLean then acquired two T-2 tankers through Pan-Atlantic and refitted them with spar decks to carry trailers. The two converted T-2 tankers, IDEAL X and ALMENA, which can carry 58 trailer units of 33 feet length on deck, became the world's first containerships when they entered service in April 1956. Together with two more converted T-2 tankers (MAXTON and COALINGA HILLS), they were deployed on Pan-Atlantic's Port Newark-Houston coastal service.

The T-2 tankers were replaced by six converted C-2 cargo ships that entered service in 1957. The converted C-2 ships can carry 226 containers of 35 feet length, stacked four high in the holds and two high on deck, and were fitted with two movable gantry cranes for self sustained cargo operations. The Port Newark-Houston service was expanded with an additional service calling Port Newark, Miami, New Orleans, Tampa, Port Newark in 1957 and a service to Puerto Rico in 1958.

From 1960, the Pan-Atlantic name was dropped and McLean adopted the name Sea-Land Service.