A Wired article discusses how things were, pre-1956:
But look back to the 1954 film On the Waterfront and you'll get a good idea of how things used to be. New York dockworker Terry Malloy (played by Marlon Brando) climbed into the rusting hulls of cargo ships and used brute muscle to move freight using nets and grappling hooks. Loading and unloading was so slow, ships might remain in port for days, even weeks. Only four decades ago, contemporary photos of Singapore's port showed shirtless workers stumbling down wooden gangplanks carrying enormous bundles of bananas on their backs. It was called break-bulk shipping.The Wikepedia article describes the advantages of containerization: first, it allows a trucker to load cargo in sealed containers directly onto a ship, and unload cargo directly back onto a waiting truck. No more messy loading and unloading of individual packages or boxes. Second, the use of sealed boxes greatly enhanced cargo security, helping eliminate the "falling off the truck" problem.
This inefficiency irked Malcom McLean, a crusty North Carolina trucker who defied convention to spark a logistics revolution that continues to reverberate today. Dubbed the Father of Containerization, he laid the foundation in the 1950s for what would arguably become the world's first truly packetized transport network.
McLean reckoned there had to be a better way of loading and unloading ships than the clumsy, slow, and theft-prone process of break-bulk. His first brainstorm: stacking sealed truck trailers on flatcars for long train journeys, trucking them only the few final miles to their destination. But the railroads weren't interested, so in 1955 he bought a small tanker company named Pan Atlantic and modified two of its ships to carry 58 detachable trailers. In order to stack the trailers, he removed the wheels and strengthened the sides. In April 1956, the first of these converted ships sailed from New York Harbor to Houston, and containerization became a sunrise industry.
So important was this simple innovation that "it is very unlikely that we would all be buying Japanese TVs, Costa Rican bananas, Chinese underwear or New Zealand lamb. In fact, globalisation would probably not exist and the World Trade Organization would have a lot less to talk about," according to this BBC article.
Simple ideas that change the world. Wish I could think of one.