A coastal defense fort on the western side Whidbey Island at Admiralty Head directly west of Admiralty Bay. When established in 1898, it had ten batteries of coast artillery and was inactive in 1950. It is now a Washington State Park and has with two restored guns. It was named by army officials for Brig. Gen. Thomas Lincoln Casey, once Chief of Engineers, U.S. Army whose father Silas Casey once commanded Fort Steilacoom.

The park, with its gun emplacements, fields, and beaches has been rehabilitated by Washington State Parks & Recreation Commission as one of Whidbey Island’s most popular attractions.