Formally commissioned in January 1944, Naval Amphibious Base (NAB), Coronado provides a shore base for the operations, training, and support of naval amphibious units on the West Coast. It is one of only two Navy amphibious training bases in the United States. NAB is approximately 1,000 acres (4 km2) in size and is composed of the Main Base, training beaches, California least tern preserve, recreational marina, enlisted family housing, and state park. State Highway 75 separates NAB into surfside (ocean) and bayside sections. The majority of the bayside is composed of fill materials dredged from San Diego Bay in the early 1940s. Amphibious training is conducted on both surfside and bayside beaches. To the south of the Main Base, the majority of amphibious training activities takes place on about of ocean beachfront property, leased from the State of California. A least tern nesting preserve is located on North and South Delta Beach between the NAB Marina and Main Base. NAB is located within the city of Coronado, California, a community of approximately 30,000. The city of Coronado covers nearly of land, and NAB lies south of the main residential and commercial portions of the city. Another naval facility, Naval Air Station (NAS) North Island, is located northwest of the city of Coronado. South of NAB is the Silver Strand.