Type C1 was a designation for cargo ships built for the United States Maritime Commission before and during World War II.

The first C1 types were the smallest of the three original Maritime Commission designs, meant for shorter routes where high speed and capacity were less important.

This design evolved as an answer to the projected needs for military transport and supply of the Pacific Ocean theater of World War II.

It was intended to formulate a merchant shipbuilding program to design and build five hundred modern merchant cargo ships to supplement and replace the World War I vintage vessels, including Hog Islander ships, that comprised the bulk of the U.S.

By the end of the war, U.S. shipyards working under MARCOM contracts had built a total of 5,777 oceangoing merchant and naval ships.

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.

The C1-M was the type with the largest production; it was a significant variation from the original C1 design in size, performance and profile; these were shorter, narrower, slower and the superstructure was farther toward the stern.

The C1-M variant used diesel propulsion exclusively, but only a single 2,000 hp range engine and without magnetic couplings.

Two of the Pusey and Jones ships were converted to PT boat tenders before entering service, including USS Cyrene.

Some of the diesel vessels were powered by 2, 6-cylinder Nordberg 2-stroke engines (Sulzer type) driving the single shaft via magnetic couplings and a reduction gear-box.

This configuration made maneuvering very easy when entering port, as one engine was run in reverse and the other ahead; change of direction was simply performed by energizing the appropriate magnetic coupling.

Converted to Troop Ships[3][2] 4 Modified and redesignated (to United States Navy) The Type C1-B ships were built in eight different yards, all but 15 in West Coast yards, all but 20 in California, the majority at Consolidated Steel Corporation in Wilmington, California.

In 1939, under the Long Range Shipbuilding Program, contracts for 38 ships in batches of 2 to 5 vessels were awarded after one round of competitive bidding.

Converted to Troop Ships[3][2][6] (all steam turbine driven) 7 Modified and redesignated (to United States Navy) (all steam turbine driven) The C1-S-AY1 subtype of thirteen ships built by Consolidated Steel Corporation was modified from the C1-B design for use as troopships by Great Britain under lend-lease called Landing Ship Infantry, Large and they were originally ordered as troopships.

The diesel (M for Motor) powered C1-M Type ships were a separate design from the C1-A and C1-B, meant for shorter runs and shallow harbors, either along the coasts, or for "island hopping" in the Pacific.

That organization used the ex "Pembina" built in Superior Wisconsin and renamed the "Spirit of Grace" until she was removed in 2006 and scrapped in 2008.