Posey Island State Park is a small, one-acre marine camping park with 1,000 feet of Shoreline
. It is located a quarter mile north of Pearl Island, near Roche Harbor, San Juan Island
. Posey Island is part of the Cascadia Marine Trail. All onshore campsites are for the exclusive use of boaters arriving by human- or wind-powered watercraft.Visitors arriving by vessels with motorboats are not permitted to camp at the park, but may use the island for day use.