The C series of ships differed from the Liberty and Victory ships. The first C series vessels were designed prior to hostilities and were meant to be commercially viable ships to modernize the US Merchant Marine, and reduce the US reliance on foreign shipping. The Liberty ships were a throwback to late 19th century British designs with reciprocating steam engines, but were very cheap to build in large quantities; Victory ships evolved from the Liberty ships but used modern turbine engines. The C series ships were more expensive to produce, but their economic viability lasted well into the late 1960s and early 1970s in military and merchant fleets. Several ships are still in operation.