The liberty ships were designed early in world war two, and were envisioned by the british. The design was handed over to the americans, who improved it somewhat. The plan was to have a more u-boat-resistant cargo ship (didnt really work too well, instead convoys with destroyer escorts were used).

between 1941 and 1945, 2710 Liberty ships were built! 2710! 
This is by far the largest single produced design of ship in human history.

They were soon followed by the improved victory ships, but fewer of them were built than liberty ships.

The 2710 ships were built in around 4 weeks each, at 18 different shipyards.

After the war, about 1/4 made up the post war cargo fleet, many were sold to Greeks and Italians. \

in the 1960's, several were converted into technical research ships.

today, 4 survive. 3 are museum ships, while one is a grounded cannery in alaska.

full interior build
most of the space is cargo hold, with most of the remaining space used for ballast.
engines and boilers are located at the center of the ship below the superstructure.
the 5 cargo holds are separated by walls which have no access between holds. cranes lift cargo out of the holds, which have 2 levels