Liberty ships were cargo ship

Cargo ship

A cargo ship or freighter is any sort of ship or vessel that carries cargo, 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...

s built in the United States during World War II. Though British in conception, they were adapted by the U.S. as they were cheap and quick to build, and came to symbolize U.S. wartime industrial output. Based on vessels ordered by Britain to replace ships torpedoed by German U-boats, they were purchased for the U.S. fleet and for lend-lease

Lend-Lease

Lend-Lease was the program under which the United States of America supplied the United Kingdom, the Soviet Union, China, Free France, and other Allied nations with materiel between 1941 and 1945. It was signed into law on March 11, 1941, a year and a half after the outbreak of war in Europe in...

 provision to Britain. Eighteen American shipyard

Shipyard

Shipyards and dockyards are places which repair and build ships. These can be yachts, military vessels, cruise liners or other cargo or passenger ships. Dockyards are sometimes more associated with maintenance and basing activities than shipyards, which are sometimes associated more with initial...

s built 2,751 Libertys between 1941 and 1945, easily the largest number of ships produced to a single design.

The production of these vessels mirrored, on a much larger scale, the manufacture of the Hog Islander ship

Hog Islander

Hog Islanders is the slang for ships built to Emergency Fleet Corporation designs number 1022 and 1024. These vessels were cargo and transport ships, respectively, built under government direction and subsidy to address a shortage of ships in the United States Merchant Marine during World War...

 and similar standardized types during World War I.