The Liberty ships were cargo ships built in the United States during World War II originally to an order placed by Great Britain to provide replacements for vessels torpedoed by German U-boats They were later used to increase the number of U.S. flag vessels and to provide further replacements for Britain under the lend-lease program.

Liberty ships were cheap and quick to build; between 1941 and 1945 2,751 of them were built by 16 American shipyards easily the largest number of ships produced to a single design. The production of these vessels in the Second World War mirrors the manufacture of similar standardised types on a much smaller scale during the First World War, in particular the Hog Island ship .

In 1936 the American Merchant Marine Act was passed, which provided for the subsidized construction of 50 commercial merchant vessels a year to be taken over by the United States Navy as naval auxilaries in the event of war. The number was doubled in 1939 and again in 1940 to finally 200 ships a year. The sophisticated designs were for a tanker and three types of merchant vessel, all to be powered by steam turbines. However because of the limited building capacity, and in particular the ability to build the many steam turbines required, relatively few of these ships were built.

Meanwhile, faced with the loss of merchant vessels to German U-boats and an increased requirement for mechant tonnage the British Government placed an order for 60 tramp steamships with American yards in 1940, to be known as the Ocean class.

These were fairly large (for the time) but simple ships with a single 2,500 horsepower reciprocating engine of obsolete but reliable design. Although the earlier designs upon which Liberty Ships were based were coal fired, the Liberty Ships themselves had oil fired boilers. The similar "Ocean" vessels built for England were coal fired, since that country had abundant supplies of coal mine but no indigenous source of oil. The predecessor designs, including the Northeast Coast, Open Shelter Deck Steamer, were based on a ship originally produced in Sunderland by J.L. Thompson & Sons in 1879, and as a 60-year old design was simple and easy to build. This type of ship had been widely manufactured until the 1930s, the last being the SS Dorrington Court . The order specified an increase in draught by 18 inches allowing a displacement increase from 9,300 tons to 10,100 tons.

The accommodation, bridge and main engine of these vessels were located in the middle of the ship. A long tunnel connected the main engine shaft to the aft part of the shaft connected with the propeller.

The design was modified by the United States Maritime Commission to conform to American construction practices and to make it even quicker and cheaper to build, and was designated EC2-S-C1 — Emergency Cargo, 2 = large ship. Welding was used extensively, and accounted for one third of the labour costs. The order was given to a conglomerate of West Coast engineering and construction companies known as the Six Companies, headed by Henry J. Kaiser and also adopted as the Merchant Marine Act design.

On 27 March 1941 the Defense Aid Supplemental Appropriations Act which increased the number of lend-lease ships to 200, and in April this was increased to 306, of which 117 would be Liberty ships.

The ships initially had a poor public image and to try to assuage public opinion, 27 September 1941 was designated Liberty Fleet Day, and the first 14 "Emergency" vessels were launched that day. The first of these was Patrick Henry, launched by President Franklin D. Roosevelt. In the speech which he delivered when launching the vessel, referred to Patrick Henry's speech of 23 March 1775 which Henry finished with the words "Give me liberty or give me death". Roosevelt said that this new class of ships would bring liberty to Europe, which gave rise to the name Liberty Ship.

On 15 October 1941 the first of the original British Ocean class ships, Ocean Vanguard was launched.

Early on, each ship took about 230 days to build (Patrick Henry took 244 days), but the average eventually dropped to 42 days. The record was set by Robert E. Peary, which was launched 4 days and 15 1/2 hours after the keel was laid, although this was a publicity stunt and was not repeated. The ships were made assembly-line style, from premade sections. In 1943, three new Liberty ships were being completed every day. They were mainly named after famous Americans, starting with the signatories of the Declaration of Independence.

Any group which raised War bonds worth $2 million could propose a name, for instance the SS Francis J. O'Gara was named for the purser of the SS Jean Nicolet who was thought to have been killed in a submarine attack but in fact survived the war in a Japanese prisoner of war camp. He was the only living person to have a Liberty ship named after him. Although most were named after people, there were exceptions such as the SS Stage Door Canteen named for the USO club in New York and the SS U.S.O. named after the organisation itself [1].

SS Carlos Carrillo

A few suffered structural problems including cracks in the deck or hull and it is reported that a very few foundered for this reason, including the SS John P. Gaines which broke in half on 24 November 1943 with the loss of 10 lives. Balancing these problems are the facts that (a) the ships were built in great haste by often inexperienced personnel, (b) they were frequently grossly overloaded, and (c) a number of the problems were associated with severe storms at sea that would have placed any ship at risk. The successor to this design, the Victory ship was both strengthened and made less stiff to address Liberty Ship structural concerns.

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 the original design life of five years, have combined to make Liberty ships a subject of much study.

Late in the war, the building of Liberty ships was replaced by that of Victory ships. Several designs of mass-produced petroleum tankers were also produced, the most numerous being the T2 tanker series with about 490 built between 1942 and the end of 1945.

The last Liberty ship constructed was the SS Albert M. Boe, launched on 26 September 1945 and delivered on 30 October 1945. She was named after the chief engineer of a United States Army freighter who had stayed in the engine room to shut down his ship's engines following an explosion there on 13 April 1945, and for which he was awarded a posthumous Merchant Marine Distinguished Service Medal [2].

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 two surviving Liberty ships are the SS John W. Brown and the Jeremiah O'Brien, both museum ships. Both ships still put out to sea regularly.

Another notable Liberty ship was SS Stephen Hopkins, which sank a German commerce raider in a ship-to-ship gun battle in 1942. She was the first American ship to sink a German surface combatant.

SS Richard Montgomery is also notable, though in a less positive way; the wreck of the ship lies off the coast of Kent with 1,500 tons of explosives still on board, enough to match a small nuclear weapon should they ever go off.

See also

• List of Liberty ships
• Category:Liberty ships

External links

• Liberty Ships built by the United States Maritime Commission in World War II
• Links to Liberty Ship information
• SS Jeremiah O'Brien website (one of two still operational liberty ships)
• SS John W. Brown website (one of two still operational liberty ships)