Portland Head Light, Maine, William Aiken Walker

Casco Bay is an inlet of the Gulf of Maine on the southern coast of Maine, New England, United States. Its easternmost approach is Cape Small and its westernmost approach is Two Lights in Cape Elizabeth. The city of Portland sits along its southern edge and the Port of Portland lies within.

European discovery

There are two theories on the origin of the name "Casco Bay". Aucocisco is the Abenaki name for the bay, which means "place of herons" (sometimes translated as "muddy").[1] The Portuguese explorer Estêvão Gomes mapped Maine's coast in 1525 and named the bay "Bahía de Cascos" (Bay of Helmets, based on the shape of the bay).[citation needed]

The first colonial settlement in Casco Bay was that of Captain Christopher Levett, an English explorer, who built a house on House Island in 1623–24. The settlement failed.[2] The first permanent settlement on the bay was named Casco; despite changing names throughout history, that settlement remains the largest city in the region, now called Portland, Maine.

Colonel Wolfgang William Römer, an English military engineer, first reported in 1700 that the bay had "as many islands as there are days in the year",[3] leading to the bay's islands being called the Calendar Islands, based on the popular myth there are 365 of them. The United States Coastal Pilot lists 136 islands;[3] former Maine state historian Robert M. York said there are "little more than two hundred islands".[4]


Native American occupation and relations

At the time of European contact in the 16th century, people speaking an Eastern dialect of the Wabanaki language inhabited present-day Casco Bay.

A number of treaties were negotiated and signed between the British colonies and members of the Wabanaki Confederacy in Casco Bay, including the Treaty of Casco (1678), the Treaty of Casco (1703), and Treaty of Casco Bay (1727).

The latter treaty was the result of a conference between the British and the Abenaki in August 1727, at which the parties agreed to uphold the terms of the 1725 Treaty of Peace and Friendship that ended Dummer's War, and to cooperate in keeping the peace. Chief Loron Sagouarram, who had signed the Treaty of 1725, addressed the gathering in 1727, giving his understanding of the Treaty relationship.[5]

During King William's War, Louis de Buade de Frontenac, the Governor General of New France, launched a campaign to drive the English from the settlements east of Falmouth, Maine.[6] On 16 May 1690, the fortified settlement on Casco Bay was attacked by a war party of 50 French-Canadian soldiers led by Jean-Vincent d'Abbadie de Saint-Castin, about 50 Abenaki warriors from Canada, a contingent of French militia led by Joseph-François Hertel de la Fresnière, and 300-400 additional natives from Maine, including some Penobscots under the leadership of Madockawando. Fort Loyal was attacked at the same time. About 75 men in the Casco settlement fought for four days before surrendering on 20 May, on condition of safe passage. Instead, most of the men, including John Swarton, were killed, and the surviving settlers were taken captive, including Hannah Swarton and her children. Swarton was ransomed in 1695 and her story published by Cotton Mather.[7]: 196–99 

War of 1812

Casco Bay is also home to abandoned military fortifications dating from the War of 1812 through World War II; during World War II, Casco Bay served as an anchorage for US Navy ships.

Civil War

Fort Gorges, on Hog Island Ledge in the middle of Portland Harbor, dates to the American Civil War.[8]

World War II

Since Casco Bay was the nearest American anchorage to the Atlantic Lend-Lease convoy routes to Britain until the U.S. entered World War II, Admiral King ordered a large pool of destroyers to be stationed there for convoy escort duty in August 1941.[9]

The State Historic Site of Eagle Island was the summer home of Arctic explorer Robert Peary.

In popular culture

Marine economy

Portland has a substantial fleet of deep-sea fishing vessels that offload their catch primarily at the Portland Fish Exchange. Numerous towns and islands serve as ports for lobster boats. Recreational fishing boats can also be chartered.

Marinas include:

During the 1980s and 1990s, Bath Iron Works operated a dry dock in Portland Harbor to repair U.S. Navy vessels.


Predominant fish in the bay include mackerel, striped bass, and bluefish. Shellfish include lobsters, crabs, mussels, clams, and snails. Harbor seals congregate on certain exposed ledges, and whales on occasion swim into the bay, and in a few instances into Portland Harbor. Seagulls, cormorants and varying species of duck are the most common birds; more rarely osprey, eagles and herons have been sighted. Casco Bay contains bay mud bottoms and banks in some locations, providing important substrates for biota.


A Casco Bay Lines ferry returning to Portland after its journey out into the bay

The bay's major islands are served by the Casco Bay Lines ferry service at the Maine State Pier in Portland. Peaks Island is served by a car ferry and sees 16 ferries a day during the summer. The other islands see fewer ferries and no car transport. Great and Little Diamond islands and Long Island are primarily served by the Diamond Pass run, which is popular with tourists in the summer. Other services Casco Bay Lines offers include a daily mailboat run, a cruise to Bailey Island, and a sunset run.

Other services such as water taxis are popular alternatives to ferries, but are limited to six passengers per boat.

Notable cities and towns

From south to north:


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Major islands

Minor islands[11]


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Casco Bay is home to 6 lighthouses:


Forts in Casco Bay:

Fort Constructed
[citation needed]
Fort Gorges 1865 Hog Island Ledge, Portland, ME
Fort Levett 1898 Cushing Island, Portland, ME
Fort Lyon 1909 Cow Island, Portland, ME
Fort McKinley 1907 Great Diamond Island, Portland, ME
Fort Preble 1808 Southern Maine Community College/Spring Point Ledge Light, South Portland, ME
Fort Scammel 1808 House Island, Portland, ME
Fort Williams 1872 Fort Williams Park, Cape Elizabeth, ME
Battery Steele 1942 Peaks Island, Portland, ME


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The newspaper for Portland, the largest city in Casco Bay, is the Portland Press Herald (Maine Sunday Telegram on Sundays). The Island Institute publishes The Working Waterfront, a free monthly newspaper reporting "the news of Maine's coast and islands". For Southern Maine news, obituaries and sports, The Forecaster is published weekly. In the early 20th century, the Casco Bay Breeze published news of the islands from 1901 to 1917. Digitized copies of it from 1903 to 1917 appear for free on the Library of Congress website "Chronicling America".[12]

See also


  1. ^ The Islands of Casco Bay, p, 4
  2. ^ James Phinney Baxter (1893). Christopher Levett, of York: The Pioneer Colonist in Casco Bay. The Gorges Society. casco bay christopher levett.
  3. ^ a b The Islands of Casco Bay, p. 3
  4. ^ "Robert York '37". abacus.bates.edu.
  5. ^ Daniel N. Paul, "Journey Of Hope - Gathering To Ratify the Treaty of 1725 at Annapolis Royal", http://www.danielnpaul.com/TreatyOf1725Ratified-1726.html
  6. ^ Maine History Online: "1668-1774, Settle and Strife," Maine Historical Society
  7. ^ Coleman, Emma Lewis. New England captives carried to Canada between 1677 and 1760, during the French and Indian wars. Portland, Maine: The Southworth Press, 1925.
  8. ^ "World War II left a big footprint on Casco Bay islands". Island Journal. 2020-07-17. Retrieved 2022-05-16.
  9. ^ Heinrichs, Waldo (1988). Threshold of War: Franklin D. Roosevelt & American Entry into WWII. Oxford: Oxford University Press. p. 165. ISBN 0195061683.
  10. ^ "Casco Bay Films: About Casco Bay". cascobayfilms.blogspot.com.
  11. ^ "Casco Bay - Not for Navigational Use!!!". Archived from the original on 2009-12-19. Retrieved 2010-08-09.
  12. ^ "Chronicling America | Library of Congress".
  13. ^ Kewaunee Communities 2025 by Jeffrey Sanders of OMNNI Associates, Inc., Chapter 1: Introduction, page 1 (page 4 of the pdf) (Archived May 14, 2022)

43°38′N 70°03′W / 43.633°N 70.050°W / 43.633; -70.050