Great Diamond Island

Fort McKinley is a former United States Army coastal defense fort on Great Diamond Island, Maine in Casco Bay, which operated from 1873 to 1947. It was named for President William McKinley. It included a sub-post, Fort Lyon, on Cow Island, just north of Great Diamond Island. Fort Lyon was named for Nathaniel Lyon. Both forts were part of the Coast Defenses of Portland, renamed the Harbor Defenses of Portland in 1925, a command which protected Portland's port and naval anchorage 1895-1950. In 1946 Fort Lyon was closed and turned over to the City of Portland. After Fort McKinley's closure it was transferred to the United States Navy, which sold the site (via the General Services Administration) to private interests in 1961. The Fort McKinley Historic District was listed on the National Register of Historic Places in 1985.

Little Diamond Island is an island in Casco Bay, Maine, United States. It is part of the city of Portland. The island was formerly known as Little Hog Island. It is mostly made up of private property, and it is a vacation destination. It can be accessed by ferry from the mainland.As of the 2000 census, the island had a year-round population of five. There are few permanent residents because the water supply is turned off during the winter.

Cow Island is a 26-acre (11 ha) island in Casco Bay, Maine, United States, off Great Diamond Island, about 3 miles (4.8 km) northeast of downtown Portland, and is part of the Town of Long Island in Cumberland County. A non-profit youth development organization called Rippleffect owns the island and has the responsibility to protect the island's natural ecosystem as well as the island's public access.

Peaks Island is the most populous island in Casco Bay, Maine. It is part of the city of Portland and is approximately 3 miles (4.8 km) from downtown. The island is served by Casco Bay Lines and is home to its own elementary school, library, and police station. It is the only island in Casco Bay that allows cars throughout the island due to its size. While small, the island hosts a variety of businesses including an ice cream parlor, restaurant, grocery store, kayak rentals, golf cart rentals, art galleries, the Fifth Maine Regiment Museum and the Umbrella Cover Museum, among others.The island was originally known as Pond Island. It became Michael's Island, after Michael Mitton was gifted the island on a sixty-year lease by his father-in-law, George Cleeve. It was subsequently named Munjoy's Island (for George Munjoy) and Palmer's Island (for Munjoy's son-in-law, John Palmer).

The Umbrella Cover Museum in Peaks Island, Maine is a museum that pays tribute to umbrella covers. The museum was created and is curated by Nancy 3. Hoffman, who has collected more than 2000 umbrella covers from 66 countries as of July 2018.The mission of the Umbrella Cover Museums states that it is "dedicated to the appreciation of the mundane in everyday life. It is about finding wonder and beauty in the simplest of things, and about knowing that there is always a story behind the cover."The idea for the museum came when Hoffman was cleaning out a closet and came across seven umbrella covers. The museum began in Hoffman's kitchen and was moved to a larger location as the collection grew. The museum's collection ranges in size from a two-and-a-half-inch Barbie doll cover to a six-foot patio umbrella sleeve. It has hosted special exhibitions including “People and Their Covers” and “New Umbrella Cover Fashions.”On 7 July 2012, Guinness World Records named Hoffman's umbrella cover collection of 730 at the time to be the largest in the world.The museum is closed during the winter. Guided tours include Hoffman, who is also a musician, singing "Let a Smile Be Your Umbrella" while playing an accordion.

Greenwood Garden Playhouse was a theater on Peaks Island, Maine, United States. Completed in 1884, as an open-air roller skating rink, it was converted to a theater in 1898. It became a dance hall prior to its closure in 1957 as a summer stock theater. Jean Stapleton's first professional appearance in the summer of 1941 was in a production at the playhouse. Martin Landau also made his professional stage debut in a 1951 production of Detective Story at Greenwood Garden, where for several seasons he was a resident cast member. Its grounds featured a carousel, a Ferris wheel and a wooden observation tower, which people paid to be able to view Mount Washington, the highest mountain in the Northeastern United States. The playhouse was located on Garden Place, just off Island Avenue, near the southwestern tip of the island. In 2021, the garden was added to the National Register of Historic Places.

Battery Steele (U.S. Army Corps of Engineers Battery Construction #102) is a United States military fortification on Peaks Island, Portland, Maine in Casco Bay. Completed in 1942 as part of World War II, it is located on 14 acres (5.7 ha) on the oceanside area of the island, formerly part of the Peaks Island Military Reservation. It is named for Harry L. Steele, who was a Coast Artillery officer during World War I. It was armed with two 16-inch MkIIMI guns and, with a 12-inch gun battery at Fort Levett on Cushing Island, replaced all previous heavy guns in the Harbor Defenses of Portland. It was built to protect Casco Bay, particularly Portland harbor, from Kennebunk to Popham Beach in Phippsburg. According to Kim MacIsaac and historian Joel Eastman in An Island at War, “Battery Steele is not only the largest gun battery built on Peaks Island, but also an example of the largest battery ever built anywhere in the United States.” In 1995, after decades of non-use, the Peaks Island Land Preserve, a community land preservation group, formed to purchase the area and forever preserve it as a public space. On October 20, 2005, the property was listed on the National Register of Historic Places. Other coast defense structures on the island include fire control towers and the counterweight for a disappearing searchlight tower (it "disappeared" when folded down).

Long Island is an island town in Cumberland County, Maine, United States, which seceded from the city of Portland in 1993. The population was 234 at the 2020 census. It is part of the Portland–South Portland–Biddeford, Maine Metropolitan Statistical Area.

The Fifth Maine Regiment Community Center is a historic building at 45 Seashore Avenue on Peaks Island, an island neighborhood of Portland, Maine in Casco Bay. It was built in 1888 by American Civil War veterans "as a memorial to their deceased comrades and as a reunion hall for themselves." It was listed on the National Register of Historic Places in 1978 and designated a Greater Portland Landmark in 1984. Today it is open as a museum.

The Eighth Maine Regiment Memorial, now the 8th Maine Lodge, is a historic summer fraternal meeting house at 13 Eighth Maine Avenue on Peaks Island, an island neighborhood of Portland, Maine. Built in 1891 as a reunion site for veterans of the American Civil War 8th Maine Volunteer Infantry Regiment, it is a fine example of Shingle style architecture, and an important work of the local architectural firm of Fasset and Tompson. It was listed on the National Register of Historic Places in 2006, and presently operates as a summer lodge and museum, with rooms rented to the public.

The Battle of Portland Harbor was an incident during the American Civil War, in June 1863, in the waters off Portland, Maine. Two civilian ships engaged two vessels under Confederate States Navy employment.

Fort Gorges is a former United States military fort built on Hog Island Ledge in Casco Bay, Maine, United States. Built from 1858 to 1864, no battles were fought there and no troops were stationed there. Advancing military technology, including iron clad ships and long range guns, rendered the fort obsolete before it could be used. The fort is now a park, accessible only by boat. It was added to the National Register of Historic Places in 1973.