U.S.S. Ranger (CV-4) was an interwar United States Navy aircraft carrier, the only ship of its class. As a Treaty ship, Ranger was the first U.S. vessel to be designed and built from the keel up as a carrier. She was relatively small, just 730 ft (222.5 m) long and under 15,000 long tons (15,000 t), closer in size and displacement to the first US carrier. An island superstructure was not included in the original design, but was added after completion.
Deemed too slow for use with the Pacific Fleet's carrier task forces against Japan, she spent most of World War II in the Atlantic Ocean, where the German fleet, the Kriegsmarine, was a weaker opponent. Ranger saw combat in that theatre and provided air support for Operation Torch. In October 1943, she fought in Operation Leader, air attacks on German shipping off Norway. She was sold for scrap in 1947.
Work began in 1925 on the design of a fourth aircraft carrier for the US Navy, as a follow-on to the small Langley, converted from a collier, and the large Lexington and Saratoga, which were in the process of being converted from incomplete battlecruisers. Carrier number four was the Navy's first opportunity to design a purpose-built aircraft carrier. Preliminary design work occurred before extensive operation of the preceding three. Having limited experience to draw on, key characteristics of the design were derived from wargaming experience at the U.S. Naval War College. During design and construction many alterations would occur as a result of increasing experience with Langley, Lexington, and Saratoga.