To realize intermodal cargo transport, all areas of the transport chain had to been integrated. It was not simply a question of putting cargo in containers. The ships, port terminals, trucks and trains had to been adapted to handle the containers.
On 26 April 1956, Malcom McLean's converted World War II tanker, the Ideal X, made its maiden voyage from Port Newark to Houston in the USA. It had a reinforced deck carrying 58 metal container boxes as well as 15,000 tons of bulk petroleum. By the time the container ship docked at the Port of Houston six days later the company was already taking orders to ship goods back to Port Newark in containers. McLean's enterprise later became known as Sea-Land Services, a company whose ships carried cargo-laden truck trailers between Northern and Southern ports in the USA.
Other companies soon turned to this approach. Two years later, Matson Navigation Company's ship Hawaiian Merchant began container shipping in the Pacific, carrying 20 containers from Alameda to Honolulu. In 1960, Matson Navigation Company completed construction of the Hawaiian Citizen, the Pacific's first full container ship. Meanwhile, the first ship specifically designed for transporting containers, Sea-Land's Gateway City, made its maiden voyage on 4 October 1957 from Port Newark to Miami, starting a regular journey between Port Newark, Miami, Houston and Tampa. It required only two gangs of dockworkers to load and unload, and could move cargo at the rate of 264 tons an hour. Shortly afterwards, the Santa Eliana, operated by Grace Line, became the first fully containerized ship to enter foreign trade when she set sail for Venezuela in January 1960.
It was a logical next step that container sizes could be standardized so that they could be most efficiently stacked and so that ships, trains, trucks and cranes at the port could be specially fitted or built to a single size specification. This standardization would eventually apply across the global industry.
As early as 1960, international groups already recognizing the potential of container shipping began discussing what the standard container sizes should be. In 1961, the International Organization for Standardization (ISO) set standard sizes. The two most important, and most commonly used sizes even today, are the 20-foot and 40-foot lengths. The 20-foot container, referred to as a Twenty-foot Equivalent Unit (TEU) became the industry standard reference with cargo volume and vessel capacity now measured in TEUs. The 40-foot length container - literally 2 TEUs - became known as the Forty-foot Equivalent Unit (FEU) and is the most frequently used container today.