Great Diamond Island is a car-free island in Casco Bay, a short boat ride from downtown Portland, best known for Fort McKinley, a turn-of-the-century Army post whose brick barracks now make up the village of Diamond Cove. For most visitors, the perfect day here is a long lunch or dinner at Diamond Cove, a look at the old fort buildings, and an easy ride back to the city.
Much of the island is private, though, and it has two separate landings, so a good visit starts with knowing which dock to use and where day visitors are welcome. Get those right and Great Diamond is one of the most rewarding half days in the bay.
At Bird's Eye Maine we run private trips across Casco Bay from Portland's working waterfront, and Great Diamond is one of the islands guests ask about most. From the water you see rows of red brick along a green parade ground, slate roofs above the cove and gulls working the ledges at low tide. Up close it feels like a small Maine village held still at the turn of the last century.
Great Diamond and Diamond Cove: Two Landings, One Island
Great Diamond is part of the city of Portland, and it sits close to Little Diamond, Peaks and Cushing at the inner edge of the bay. The thing that confuses most first-time visitors is that the island has two landings, and they serve very different parts of the island.
The Diamond Cove Landing
Diamond Cove is on the northeastern side of the island, on the old Fort McKinley grounds. Step off the dock here and you are a few minutes' walk from the restaurant, the general store and the restored fort buildings. For a dining or history day, this is almost always the landing you want.
The Great Diamond Landing
The other landing serves the island's residential neighborhood of private summer and year-round homes, away from the fort. It suits people visiting friends or staying in a rental on that part of the island, rather than day visitors heading for Diamond Cove.
Getting There From Portland
You can reach Great Diamond on the public ferry from Portland's Old Port or by private boat. If you take the ferry, read the schedule carefully, because not every run calls at both landings, and timetables change with the seasons. Check the current schedule before you go, and make sure both your outbound and return boats stop where you need them to.
Our year-round private water taxi lists Great Diamond and Diamond Cove as separate stops, with listed rates of $65 and $75. We leave from Fore Points Marina on Portland's East End and run you straight to the dock you need, which helps for a dinner reservation that runs late or a group with bags heading for the inn.
The Story of Fort McKinley
Fort McKinley is a remarkably intact coastal Army post. Around 70 structures went up here between the 1890s and World War II, and walking among them still feels like stepping into a garrison town.
From Artists' Retreat to Army Post
Before the soldiers came, Great Diamond was a summer retreat for artists and writers, and visitors are said to have included Henry Wadsworth Longfellow and Harriet Beecher Stowe. Construction of the fort began in 1891, part of a wave of new coastal defenses guarding the deep-water approaches to Portland Harbor. In 1902 the post was named for President William McKinley, a year after his assassination.
Life at the Fort
At its height, the fort's barracks and officers' quarters could house close to 1,000 soldiers, and the post had its own storehouses and blacksmith shop. The big guns sat in concrete batteries in the woods at the island's eastern end, aimed out toward the channels into the bay.
Decline and Revival
Air power made coastal forts like this one obsolete, and Fort McKinley was left behind after World War II. The buildings sat empty for decades, slowly falling apart, until a long restoration turned them into homes with slate roofs and wide porches. The old quartermaster's storehouse became the restaurant, and the blacksmith shop became the general store. The fort's historic district is listed on the National Register of Historic Places.
Long before any of this, the island was Wabanaki homeland. A prehistoric shell midden on Great Diamond, recorded as the Great Diamond Island Site, shows generations of shellfish gathering along the shore. Middens are protected archaeological sites, so leave any shell deposits you spot undisturbed.
What to Do at Diamond Cove
Diamond Cove is a private community, but day visitors are welcome at its restaurant and general store, and it is a lovely place to spend a few unhurried hours.
Lunch or Dinner at Diamond's Edge
Diamond's Edge Restaurant sits just up from the dock, inside a restored fort building looking across the water. The menu leans on Maine seafood, and on a warm evening the tables by the cove are hard to beat. Island restaurants keep seasonal hours, so call ahead and book a table before you set your boat times.
Seeing the Fort Grounds
Beyond the dock, restaurant and store, Diamond Cove is private property, and the parade ground and officers' row are best seen on a guided grounds tour arranged by reservation. It is the step most day-trippers skip, and it is well worth planning ahead for if history is the reason you are going.
Staying Overnight
The Inn at Diamond Cove offers rooms in the restored fort buildings, which gives you the parade ground at dusk and the cove at sunrise after the day boats have gone. No cars come to the island, so you leave yours in Portland. Check the inn's current policies before you book.
Getting Around the Island
Residents get around by golf cart, bike and on foot, since there are no regular cars on Great Diamond. The first thing guests notice is the quiet: wind in the spruce, halyards ticking against masts in the cove, the odd golf cart humming past.
Seeing Great Diamond From the Water
Because so much of the island is private, the water is often the best vantage point. From a boat you can idle off the eastern shore and pick out the concrete batteries among the trees, then swing around to see the long rows of barracks facing the cove, a view that is hard to get on foot. It fits naturally into our private History Tour, which follows the bay's forts and watch towers, or an Island Hopper that adds lunch ashore. You'll find both on our private tours page.
If you enjoy harbor forts, Fort McKinley pairs well with Fort Gorges, the granite fort on its own ledge closer to town. And since Great Diamond's beaches mostly sit on private land, families after barefoot beach time might add a private beach reached by boat to the same day.
Planning Your Day
A relaxed half day might look like this: leave Portland late morning, circle the island to see the fort from the water, land at Diamond Cove for lunch, join a grounds tour if you reserved one, then head home or carry on to another island. Whatever you choose, lock in your return time before your first drink is poured.
Pack a light jacket and sunglasses, because the bay runs cooler than downtown even in July, and fog can roll in fast. On our boat, snacks and drinks are welcome (no glass or red wine), and there is no bathroom aboard, so use the private restrooms at the marina before you set off.
Frequently Asked Questions
Is Great Diamond Island private?
Partly. Diamond Cove is a private community where day visitors are welcome at the restaurant and general store, with grounds tours by reservation. The rest of the island is a residential neighborhood of private homes.
Are Great Diamond and Diamond Cove different stops?
Yes. Diamond Cove is the landing for the restaurant, store and fort, while the Great Diamond landing serves the residential side of the island. Ferry runs do not always call at both, and our water taxi lists them as two separate stops.
Can you eat at Diamond's Edge without staying overnight?
Yes, day visitors arriving by ferry, water taxi or private boat are welcome. Book ahead and confirm seasonal hours, then plan your boat times around your table.
Can you visit the Fort McKinley gun batteries?
The batteries sit on private land in the woods and are not open for visitors to wander. The best way to see them is from the water, where you can make out the concrete through the trees.
Can you bring a car to Great Diamond Island?
No. The island is car-free, and residents use golf carts, bikes and their feet. Visitors leave their cars in Portland.
If you'd like to see Fort McKinley from the water and then sit down to lunch at Diamond Cove, our Island Hopper and History Tour were made for days like that, or our water taxi can simply run you over to the right landing. Nobody else joins your trip: it's your group of up to 6 and your own captain, going where you want to go. Call 207.632.9369 or email info@birdseyemaine.com and Captain Matt will plan the day with you.
