Posey Island State Park in San Juan County, Washington is a marine camping park in the Washington State Park System. It consists of 1 acre (0.40 ha) Posey Island, with about 1,000 feet (300 m) of saltwater shoreline. It is located .25 miles (0.40 km) north of Pearl Island, near Roche Harbor, San Juan Island. The park is part of the Cascadia Marine Trail and all campsites are restricted to visitors arriving in human- or wind-powered watercraft.
Coordinates: 48°37′06″N 123°10′04″W / 48.618433°N 123.167688°W