The Crater-class cargo ship were converted EC2-S-C1 type, Liberty cargo ships, constructed by the United States Maritime Commission (USMC) for use by the US Navy during World War II. The designation 'EC2-S-C1': 'EC' for Emergency Cargo, '2' for a ship between 400 and 450 ft (120 and 140 m) long (Load Waterline Length), 'S' for steam engines, and 'C1' for design C1. The class was named for the lead ship of its type, USS Crater (AK-70), with most ships in the class being named for astronomical bodies. Its 65 hulls were among the largest US Navy cargo ship classes.