 Fort Flagler was one of three forts, along with Fort Worden (near Port Townsend) and Fort Casey (on Whidbey Island), that guarded the entrance to Puget Sound.Mystery Bay State Park is another state park on Marrowstone Island, located on 10 acres (4 hectares) of Mystery Bay shorefront about a half-mile north of the Nordland General Store.It is primarily for boaters.