The Liberty ships were built as part of a WWII era program to increase the number of U.S flag cargo ships.
The project was was managed by Henry Kaiser.
Liberty ships were slow but economical to build. Hundreds of them were built by major shipyards and by emergency shipyards that had been set up to fill the need for cargo ships.
The first Liberty ship was the Patrick Henry, launched 7 September 1941. Early on, each ship took about 230 days to build, but the average eventually dropped to 42 days, with the record being set by the Robert G. Peary, which was launched 4 days and 15 1/2 hours after the keel was laid. In 1943, three new Liberty ships were being completed every day. They were all named after famous Americans.
Many Liberty ships survived the war, and made up a large percentage of the postwar cargo fleet. The term "Liberty-size cargo" for 10,000 tons may still be heard in the shipping business.
The success of the immense effort to build Liberty ships, the sheer number of ships built, and the fact that some of the ships survived far longer than they had been designed to, have combined to make Liberty ships a subject of much specialized study.
Late in the war, the building of Liberty ships was replaced by that of Victory ships and other more substantial types of cargo ships.
The two remaining liberty ships are the Jeremiah O'Brien and the John. W. Brown.
The Jeremiah O'Brien is converted into a museum ship.
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