Posey Island Marine State Park

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An itty-bitty island hides in plain sight, between Pearl Island and Roche Harbor in the San Juan archipelago. 

Posey Island Marine State Park is popular with kayak groups and porpoises, but, depending on the day, you may also have the place to yourself. 

Though Posey seems barren at first, a thorough perusal reveals meadow grasses, ancient Yew trees, bright orange lichen and wildflowers blooming in season. Photographers and painters have found endless creative opportunities here.

Ready for a hard paddle? Take your kayak for a spin around Spieden Island and its neighboring rock formations. Look for antelopes and longhorn sheep on savannah-like Spieden Island, once a game park. Though you cannot land on the privately owned island, wildlife is often visible from the water.

At the end of the day, retire to one of Posey Island’s two group campsites, each with a sweeping view. Grill up a hearty meal, sit back for a big-sky cloud show or a glorious sunset and enjoy a rare opportunity to do nothing but rest.

Park features


Posey Island Marine State Park is a 1-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. There is no potable water on the island, and visitors must pack out what they pack in. Camping reservations are required for both campsites, which are for the exclusive use of boaters arriving by human- or wind-powered watercraft.

A paddle around the northwest side of Spieden Island should not be attempted during tidal shifts, as the waters are unpredictable and dangerous. 

Please do not approach rock formations where harbor seals are resting; their undisturbed naps out of water are critical to their health and safety. 

  1. Activities
  2. Boating
  3. Camping
  4. History

Picnic & day-use facilities


Visitors arriving by vessels with motorboats are not permitted to camp at the park, but may use the island for day use. There is no potable water or garbage service to the island. Visitors must pack out what they pack in. There is one composting toilet.