Things to do nearGreat Diamond Island
Great Diamond Island is a peaceful car-free retreat in Casco Bay, Maine, known for its scenic shoreline, historic fort, and unhurried village atmosphere.
Great Diamond Island sits in Casco Bay off the coast of Portland, Maine, one of several island communities reachable by the Casco Bay Lines ferry. The island's history is shaped largely by Fort McKinley, a coastal defense installation built in the 1890s that served through both World Wars before being decommissioned.
Today the fort's handsome brick barracks and officers' quarters have been carefully converted into a private residential community, giving the island a distinctive architectural character unlike anything on the mainland. Visitors can admire the exteriors while walking the perimeter roads.
The natural landscape is just as compelling. Rocky beaches, tidal pools, and stands of spruce and pine cover much of the island's interior and shoreline. Kayakers paddle the surrounding waters, and the views across the bay toward the White Mountains on a clear day are genuinely memorable.
Great Diamond Island offers a rare chance to experience island life close to a city without the crowds of more famous destinations. Its combination of preserved history, natural beauty, and car-free tranquility makes it a rewarding half-day or full-day excursion from Portland.
7-day forecast
Chance of rainTips for visiting Great Diamond Island
Take the Casco Bay Lines ferry from Portland for the most scenic approach to the island, especially on a clear morning.
Wear sturdy shoes for walking the island's unpaved paths and uneven shoreline terrain.
Visit in late spring or early fall to enjoy the scenery with fewer day-trippers and more comfortable temperatures.
Look for Fort McKinley, a late-19th-century military installation whose brick buildings have been preserved and converted into private residences.
Bring your own food and water, as dining options on the island are limited and the ferry schedule governs your return time.
Top tours & experiences near Great Diamond Island
Cruise Casco Bay on a Private 6-Hour Charter
Book a private 6-hour powerboat cruise for up to 6 in Casco Bay
Cruise Casco Bay Lighthouses & Islands From Portland
Cruise Casco Bay by powerboat with a max of 6 guests
Cruise Casco Bay From Portland on a Private 3-Hour Charter
Charter a private 3-hour Casco Bay cruise for up to 6, with lighthouses and island views
Cruise Casco Bay on a Private 4-Hour Charter
Book a private 4-hour powerboat cruise for up to 6 in Casco Bay
Cruise Casco Bay on a Private 2-Hour Powerboat
Take a private 2-hour cruise for up to 6 in Casco Bay
Cruise Casco Bay at Sunset From Portland
Cruise Casco Bay at sunset on a classic Maine-built powerboat
Cruise Casco Bay on a Private Sunset Charter
Private 2-hour sunset cruise for up to 6 in Portland Harbor and Casco Bay