Green Island Preserve
A 48-acre island in Merchant Row with an old granite quarry pond you can swim in. Access by boat only — paddle or hitch a ride. The quarry granite supplied Rockefeller Center. The water is clearest in August.
Green Island is a Maine Coast Heritage Trust preserve (not IHT) about three-quarters of a mile offshore from Stonington Harbor, sitting in the middle of Merchant Row between Stonington and Isle au Haut. Getting there requires a boat — the closest public launch is the Colwell Boat Ramp behind Isle au Haut Boat Services on Seabreeze Avenue.
Once on island, you come ashore via a ladder on the old granite wharf on the southeastern cove. A short loop trail — about five minutes — leads through the woods to the swimming quarry. The quarry is an old granite operation whose stone reportedly went to sites including Rockefeller Center and Boston's Museum of Fine Arts. Today it's a granite-rimmed pond, good for swimming and jumping from the edges. Water warms up through summer and is at its best in August. The bottom and walls are stone, with some loose pieces and metal objects — watch where you step and land.
The preserve has a small meadow and the island's bold granite shoreline to explore. No camping permitted. Carry out everything you bring in.
What Visitors Say
"Great Skinny Dipping"
Local Tips
- Bring your own boat or kayak — there's no ferry to Green Island itself.
- Sea Kayak Stonington runs guided trips through Merchant Row; ask if Green Island is on the route.
- Check tides before landing — the granite wharf ladder gives access from certain water levels.
- Quarry swimming: jump from lower edges, not the high ones; loose stones and metal debris make the margins uneven.
- No lifeguards. Cold water. Plan accordingly.
- Warmest swimming: mid-to-late August.
Connected To
- Sea Kayak Stonington — guided archipelago trips through Merchant Row; best way to access the area without your own boat
- Sand Beach — nearest shore-accessible beach; also a gateway point for Merchant Row exploration
- Stonington Public Landing — main harbor departure point; closest launch point for water-based access