A cargo ship or freighter is any sort of ship that carries goods and materials from one port to another. Thousands of cargo carriers ply the world's seas and oceans each year; they handle the bulk of international trade. Cargo ships are usually specially designed for the task, being equipped with cranes and other mechanisms to load and unload, and come in all sizes. Specialized types of cargo vessels include container ships and bulk carriers. ( Tankers and supertankers are also cargo ships, although they are habitually thought of as a separate category. )
A beached schooner barge. Compare the hull form with a square barge.
The schooner barge was the final development of the working sailing ship. The design originally evolved in the 1870s on the Great Lakes, where it was found that sailing ships could be more profitably towed from place to place than sailed. No longer subject to the vagaries of the wind, such trips could be made on a scheduled basis, and with reduced labor costs. The idea spread into general use, resulting in the conversion of many sailing ships into barges. Ironically, most of the vessels that were converted to schooner barges were not actually schooners, but square-rigged ships. Square-riggers, with their large and expensive crews of skilled sailors, became uneconomical to operate in the face of ever-improving steam power, while more efficient schooners managed to compete for a few years longer.