The Casco Bay Watershed boasts 785 islands, islets, and exposed ledges.

Major Islands
(Island descriptions provided by Casco Bay Island Alliance.)

Chebeague (pronunciation: “shuh big” (without a significant emphasis on either syllable)  is the largest island in Casco Bay at almost five miles long and 1½ miles wide. It is home to over 360 year-round people and more than 1,600 summer residents. Its name means “isle of many springs.” It is served by Casco Bay Lines which calls at Chandler Cove on the southern end of the Island and by Chebeague Transportation Company which runs from Cousins Island to the Stone Wharf on Chebeague.


Cliff Island sits approximately six miles offshore and is the outermost island served by the Casco Bay Lines ferry service. Cliff Island boasts a year round population of approximately 60 people, the smallest of the Casco Bay inhabited islands.  In the summer, it grows to about 200. Originally named “Crotch Island” for its H-shape and natural harbors, the name was changed in 1892 when the island got its first post office. Cliff Island has extensive property under conservation trust, permanently protecting its rural atmosphere. The island is the only year-round island in Casco Bay that has no paved roads and, while cars are allowed, most people walk, bicycle, or use golf carts for transportation.  A barge ramp was added in 2008 to ease delivery of trucks and heavy items.

Great Diamond
Great Diamond Island is located 4 miles off the coast of Portland and has the smallest year round population of the islands serviced by Casco Bay Lines.  This quiet island’s population swells from a low of 50 in winter to 600 in summer.  With less than a square mile of area the island is crisscrossed with miles of dirt roads and foot paths, and is graced by 23 acres of protected Old Growth Forest.  The island is a granite outcropping with numerous small wet sand coves and a few small white sand beaches.

Little Diamond


Little Diamond Island formerly known as Little Hog Island is part of the City of Portland and is the closest island community to Portland.  At low tide it is connected by a sandbar to Great Diamond. The Northwest portion of the island was subdivided in the late 19th century and is now a summer community of about 55 cottages served by Casco Bay Lines. Most of the remainder of the island was owned until the early 21st century by the Sisters of Mercy order who operated a seasonal orphanage and retreat house there.

Long Island is located 6 miles off the coast of Portland, accessible by Casco Bay Ferries (about 45 minutes), water taxi or private boat.  The island is 3 miles long and 1 mile wide, and has a winter population of 210 (according to the 2010 census), swelling to over 1000 in the summer. Many residents, summer and winter, work in the lobster industry. Long Island claims the best sand beaches in the bay, including South Beach, a state beach. The island has a “west end” and an “east end” with a conservation area in the center.

Peaks Island, the most populous of the Casco Bay islands, is home to some 1,000 year round residents and an additional 4,000 or so summer residents.  It is a favorite summer destination for thousands of day-trippers and vacationers. It lies about 3 miles east of and a 15 minute ferry ride from Portland, Maine. The harbor side of this 720 acre island is where most of the year-round homes, businesses and civic departments are located. The interior and backshore are heavily forested with many newer homes scattered along the shore. A large portion of the forested area is protected by conservation easements.  In 1834 Peaks officially became a neighborhood in the City of Portland.

Organizations serving the islands:

Casco Bay Islands Alliance (CBIA)
CBIA is focused on enhancing and protecting the quality of life on the Casco Bay islands, and, toward that goal, makes small grants each year to island non-profits which are also working toward that end.
P.O. Box 7662, Portland, ME 04112

Chebeague & Cumberland Land Trust
The Mission of the Chebeague & Cumberland Land Trust is to preserve and protect the intrinsic values and public benefits of the natural resources in the towns of Chebeague and Cumberland.
217 Commercial Street, Suite 302, Portland, ME, 04101

Chebeague Island Community Association (CICA)
The Chebeague Island Community Association’s mission is to ensure the viability of Great Chebeague Island as a year-round community.

Cliff Island (Town of)

Island Institute
The Island Institute works to sustain Maine’s island and remote coastal communities, and exchanges ideas and experiences to further the sustainability of communities here and elsewhere.
386 Main Street
Rockland, Maine  04841

Long Island Civic Association
Their mission is to protect lands for future generations, preserve their small town and better life, and to support the community through events that bring them together.
PO Box 307, Long Island, Me, 04050

Maine Island Trail Association
The Maine Island Trail Association’s goal is to establish a model of thoughtful use and volunteer stewardship for the Maine islands that will assure their conservation in a natural state while providing an exceptional recreational asset that is maintained and cared for by the people who use it.
100 Kensington St, 2nd Floor, Portland, ME 04103

Oceanside Conservation Trust
The mission of Oceanside Conservation Trust of Casco Bay is to facilitate the conservation of wild or undeveloped open space, scenic areas, and historic landmarks in the Casco Bay region; foster low-impact and respectful access to these resources; and enhance the cultural, economic and civil well-being of residents and visitors.
(207) 699-2989

Peaks Island Community Website

Peaks Island Council
The Peaks Island Council was established by the City Council of Portland, Maine.

Peaks Island Land Preserve
Peaks Island Land Preserve is committed to the acquisition, preservation and stewardship in perpetuity of Peaks Island lands for the use and enjoyment of islanders and visitors.
P.O. Box 99, Peaks Island, ME 04108