Until the 1960s, nearly all international cargo was delivered to the dockside in small packages and shipped on break-bulk ships. They came in boxes, crates, barrels, and drums and loaded on board ship, stowed, and, at the end of the voyage, unloaded individually. This process was complicated and time consuming and exposed cargo to damage and theft.
The container revolution involved the introduction of truck-trailer-size boxes as cargo containers. These standardized containers can be filled with cargo at the farm, factory, or loading depot and then sealed and taken by truck, train, or barge to a port where it is put on board a ship. This change greatly reduced cargo handling time (it costs much less to load and unload containers by crane than it is to load and unload individual packages). Containers also eliminated costs associated with shoreside warehouses to protect conventional cargo from the weather. Export costs relating to crating and packaging as well as potential loss or damage to cargo are substantially reduced.
In typical container transportation, the shipper puts individual packages or cartons in a container, usually at an inland facility, and then the container is moved by rail or truck to a container yard close to a seaport. Once the ship arrives, the container is pulled by a tractor alongside the ship and placed on board the container ship by cranes. Container ships have specially built vertical cells that are designed to firmly hold the containers in place during the voyage. Today more than 90 percent of world trade is moved in containers. Only a handful of commodities are shipped in break-bulk: steel, paper, plywood. Even rubber and cocoa beans, which were largely shipped in break-bulk, are now moved in containers. The container revolution necessitated the development of port infrastructure such as dockside cranes and standardized containers, including connections to railways and highways, as well as the designation and building of specific areas for containers.
Source: Seyoum Belay (2014), Export-import theory, practices, and procedures, Routledge; 3rd edition.