Great Diamond Island

A Fort Turned Island Community

Great Diamond Island sits in inner Casco Bay, a 20-minute ferry ride from Portland. It is a small island with a split personality. The northern end has a traditional year-round community of shingled cottages and quiet roads. The southern end, known as Diamond Cove, is a gated community built on the grounds of Fort McKinley, a turn-of-the-century military installation whose barracks, officers’ quarters, and support buildings have been converted into homes, an inn, and restaurants.

Construction of Fort McKinley began in 1897 and was completed by 1906. Named for President William McKinley, the fort served as a key military installation through both World Wars, defending Portland Harbor with coastal artillery. After the military left, the property was converted to private use in the 1980s. Today, the red-brick barracks and granite buildings house condominiums, and the parade grounds and military roads have become the streets of a residential community where golf carts are the primary mode of transportation.

The fort’s architecture is well-preserved and visually striking. Walking through Diamond Cove feels like walking through a military base that has been reimagined as a coastal village.

Diamond’s Edge Restaurant

Diamond’s Edge Restaurant, located at the ferry dock on the island’s southern side, is the main reason day-trippers visit Great Diamond. The waterfront restaurant serves seafood and cocktails with views of the harbor and passing boats. It is open to the public and accessible directly from the Casco Bay Lines ferry dock. No need to enter the gated Diamond Cove community.

The restaurant operates seasonally, typically from June through October.

Fort McKinley and Diamond Cove

The Diamond Cove community occupies the former Fort McKinley grounds. While the residential area is gated and not generally open to the public, the Inn at Diamond Cove welcomes overnight guests and diners. The inn occupies restored military buildings and offers a more immersive experience of the fort’s architecture and setting.

From the public areas near the docks and restaurant, you can see the red-brick barracks, the parade ground, and the overall layout of the fort. The military architecture is distinctive and well worth seeing, even from the outside.

Exploring the Island

Great Diamond is small. The walk from one end to the other takes about 30 minutes. The roads are narrow and quiet, with golf carts the most common vehicle. Picnic areas and hiking trails allow you to take in the shoreline, spruce groves, and views across the bay.

The island has no cars for visitors. Walk, or simply enjoy the compact scale.

Getting There

Casco Bay Lines operates the ferry from 56 Commercial Street in Portland. Great Diamond is served by the same down-bay runs that go to Long Island, Chebeague, and Cliff Island. The crossing to Great Diamond takes approximately 20 to 25 minutes.

Peak-season adult fares are approximately $16 round trip. Off-peak fares are approximately $8.50. Check the schedule for Great Diamond stops, as not every departure serves this island. Some runs stop at the Diamond Cove dock (south end) and others at the Great Diamond dock (north end).

When to Go

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