The US Navy has eight dock landing ships (LSD) that support amphibious landing operations by transporting Landing Craft Air Cushing (LCAC), conventional landing craft, helicopters, and other equipment onto hostile shores. Unlike the amphibious transport dock (LPD), LSD ships are designed to carry more and larger military vehicles and assets as well as capable of launching craft with their crews during amphibious assault operations and providing docking and repair services.
The development of the ship was first conceived sometime in the World War II era and was further expanded in the early 1950s when the Navy decided to build a new class with redesigned superstructures and improved hull lines, the Thomaston-class (LSD-28). This ship class served the branch for three decades before it was decommissioned and replaced by the Whidbey Island-class (LSD-41), specifically designed to operate LCAC vessels. In addition, the fifth-generation LSD featured more significant improvements, facilities, and technologies (such as additional cranes, communication, and combat systems) than its predecessors.
The fleet was introduced in 1985, built by Lockheed Shipbuilding (Seattle) for the first three ships and Avondale Shipyard (now Huntington Ingalls Industries) for the remaining five for the US Marine Corps. It has the largest capacity, with a well deck measuring about 131.1 meters (430 feet) by 15.2 m (50 ft), capable of fitting at least four LCAC hovercraft—five if the vehicle ramp is raised. It can also accommodate 21 Landing Crafts (LCM), three Landing Craft Utilities (LCU), or 64 Assault Amphibious Vehicles (AAV).
Furthermore, the ship is outfitted with multiple cranes and a shallow draft, making it ideal for amphibious operations. The overall measurement of each Whidbey Island-class is about 609 ft (185.6 m) in length, 84 ft (26 m) beam, and a displacement of 15,939 tons (16,194.79 metric tons) full load.