Posey Island Marine State Park

By Sarah MitchellOutdoor Editor & Trail ExpertMay 8, 2026 · Updated May 12, 2026

🏆🏆🏆🏆🏆 Smallest Marine Park — Just 1 acre! — The SMALLEST state park in Washington, a tiny rock island in the San Juans with camping for just 16 people

Posey Island Marine State Park is the smallest state park in Washington — just 1 acre of rocky island in the San Juan Islands near Roche Harbor. Despite its tiny size, the island offers 2 campsites for up to 16 people — making it one of the most intimate camping experiences in the Pacific Northwest. The island is accessible only by kayak or small boat. Named for the wildflowers (posies) that bloom on the island in spring, this miniature park offers big views of the San Juan archipelago and the Olympic Mountains beyond.

Visitor Information

About Posey Island

Posey Island Marine State Park is the smallest island park in the Washington state park system — just one acre! Located in the San Juan Channel near Roche Harbor on San Juan Island, the tiny island offers a uniquely intimate camping experience. Only 16 people are allowed on the island at once, ensuring a private island experience.

Things to Do

Boat-in or kayak-in camping on your own private island (2 primitive campsites, max 16 people), kayaking, crabbing, and watching boat traffic in the San Juan Channel. It’s the ultimate “private island” experience on a state park budget.

Insider Tips

Smallest state park: Posey Island is one of Washington’s smallest state parks — just 1 acre in the San Juan Islands. Pro tip: The tiny island has one campsite — reservable in advance, it’s arguably the most exclusive camping spot in Washington. Kayak camping: The San Juan Islands offer world-class kayak camping — paddle between marine state parks on multi-day trips.

Best Time to Visit

Summer: Peak kayak camping season. Fall: Quiet paddling. Spring: Low tides reveal marine life. Winter: Not recommended for camping.

Frequently Asked Questions

Can I camp on a 1-acre island?

Yes — Posey Island’s single campsite accommodates up to 16 people. It’s boat/kayak access only — no water, no facilities beyond a composting toilet. Bring everything you need, including water. The experience of having an entire island to yourself — surrounded by orcas, eagles, and seals — is unforgettable. Reserve well in advance for summer weekends.

More parks nearby: Posey Island SMP is a short drive away, while Stuart Island Marine State Park lies a short drive away.

Wildlife & Nature

Posey Island Marine State Park — a 1-acre island in the San Juan Islands near Roche Harbor — is one of the smallest state parks in Washington. The island accommodates just 2 campsites. Harbor seals rest on nearby rocks. Bald eagles soar overhead. The tiny island offers an intimate, uncrowded camping experience surrounded by the rich marine waters of the San Juan archipelago.

Nearby Attractions

Roche Harbor — 0.5 miles southeast on San Juan Island — has a resort, marina, sculpture park, and the historic Hotel de Haro (1886). English Camp (San Juan Island NHP) — 3 miles south. Friday Harbor — 10 miles south — has the Whale Museum. Stuart Island is 3 miles northwest.

About the Author

Sarah Mitchell

Outdoor Editor & Trail Expert

Sarah Mitchell is an outdoor writer and trail researcher with over 8 years of experience exploring state parks across America. As the lead editor at AmericasStateParks.org, she has personally visited more than 200 parks in 42 states, logging thousands of trail miles and hundreds of campground nights. Sarah specializes in detailed park guides, accessibility information, and family-friendly outdoor planning. Her work focuses on helping first-time visitors feel confident and well-prepared for their state park adventures.

200+ state parks visited across 42 states | 8+ years of outdoor writing

View All Articles by Sarah Mitchell →