Umbrella Cover Museum

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).

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.

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.

House Island is a private island in Portland Harbor in Casco Bay, Maine, United States. It is part of the City of Portland. The island is accessible only by boat. Public access is prohibited, except for an on-request tour sanctioned by the island's owners. House Island includes three buildings on the east side and Fort Scammell on the west side. The buildings are used as vacation rentals and other summer residences. The island's name derives from the site of an early European house, believed that built by Capt. Christopher Levett, an English explorer of the region.[1][2]The island sold for $5.35m in 2022.

Fort Levett was a former U.S. Army fort built on Cushing Island, Maine, beginning in 1898. Located in Cumberland County, Maine, in Casco Bay near Portland, Maine, the fort was heavily fortified with guns for coastal defense. Conceived under the Endicott Program in 1885 and begun in the wake of the Spanish–American War, Fort Levett was manned during both world wars. It was part of the Coast Defenses of Portland, later renamed the Harbor Defenses of Portland, a command which protected Portland's port and naval anchorage 1904-1950. The fort's name is sometimes misspelled as "Fort Leavitt".

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.

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).

Cushing Island, or Cushing's Island, is a privately owned island in Casco Bay in the U.S. state of Maine. Part of the city of Portland, roughly 45 families live there seasonally.

Great Diamond Island is an island in Casco Bay, Maine, United States. It is part of the city of Portland. At the 2000 census, the island had a year-round population of 77. The island is not accessible from the mainland by motor vehicle and has a limited network of roads. The primary modes of transportation are golf carts and bicycles. This fact has become a selling point for the island, marketing the area as "car free" and "kid friendly". The island was used as a military base starting in the late 19th century and continuing through World War II. After the base was decommissioned, the bunkers and residences were left idle for over 30 years before being developed and sold to private citizens.

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.

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.