[11] Around 14,000 BCE during the Wisconsin glaciation period at the end of the last glacial cycle, the Laurentide ice sheet covering the Casco Bay region began to recede, according to radiocarbon dating on marine shells and other materials.
[25] In a 2019 study of invasive species threatening Casco Bay eelgrass and kelp beds that other organisms and wildlife depend on, researchers found abundant evidence of the presence of several types of tunicates, bryozoa, Japanese skeleton shrimp and at one location European green crabs.
[26] Casco Bay has an estimated 16,655 acres of intertidal habitats to include mudflats, marshes, beaches and rock formations according to the National Wetlands Inventory,[27] supporting a range of biota and wildlife.
Among more than three dozen species of fish found commonly in Casco Bay are bluefin tuna, bluefish, cod, herring, mackerel, menhaden, sharks, smelt, striped bass, and winter flounder.
[32] At the time of European contact in the 16th century, Abenaki peoples inhabited the region of present-day Casco Bay, including members of the Almouchiquois or Aucocisco group in the vicinity of the Presumpscot River.
[58] In 1642, Cleeve, Tucker, Mackworth, Royall and Smith were among 30 signers of a petition to the British House of Commons asking for relief from administrators assigned by Gorges to the region who were exercising "unlawful and arbitrary power and jurisdiction over the persons and estate of your petitioners and the said other planters to their great oppression utter impoverishment and the hindrance of the plantation in these parts".
[64] Spurred by the Wampanoag chief Metacom in what came to be known as King Philip's War, Native American warriors attacked colonial farms and settlements along the New England coast and inland areas beginning in June 1675, including in the Casco Bay region.
If prodded into action by Metacom's militant contemporaries drumming up support in northern New England, many local tribes followed their own counsel in planning attacks in the regional conflict that some historians dub the First Abenaki War,[65] or chose not to initiate hostilities.
[68] After colonial militia leader Richard Waldron laid a trap under the guise of peace talks to capture several Wabanaki warriors who were then executed or enslaved, tribes intensified attacks on settlements throughout Maine, causing most settlers to flee south.
In August 1688, in response to an English colonial raid of Penobscot Bay settlements, French officer Jean-Vincent d'Abbadie de Saint-Castin led counter-raids by Acadian militia and Wabanaki Confederacy warriors, including at Yarmouth.
[77]: 196–99 Church returned to Casco Bay in September 1690 with a contingent of about 300 volunteer militia and indigenous warriors, launching attacks up the Androscoggin River and overseeing the brutal killings of Native Americans who had been left behind in a village, then pulling back to Cape Elizabeth.
[89] The booming wood trade helped create cottage industries, with exports bringing in money to fund extensive construction, including churches, inns, assembly halls, and infrastructure, like bridges.
[94] On March 2, 1775, the Brunswick Continental Association leader Samuel Thompson invoked the boycott in attempting to block a ship from unloading rigging and other maritime supplies, with HMS Canceaux dispatched from Boston to Falmouth to provide protection.
After delivering an ultimatum for Falmouth denizens to surrender all arms and swear allegiance to King George III, he allowed time for residents to flee parts of the town within cannon range before opening fire.
[99] In April 1778, the French frigate La Sensible arrived in Casco Bay with a communique of France's commitment to a treaty that would result in extensive military and logistics support for the Continental Army, including naval power to hamper British movements.
[119] Portland became the home port for at least nine privateers operating against British merchant shipping, including the 16-gun brig True-Blooded Yankee, which conducted several raids along the coasts of Ireland and Scotland before being captured.
[124] The war prompted a fresh review of coastal fortifications by the U.S. Army Corps of Engineers,[125] which eventually resulted in the construction of Fort Gorges on Hog Island Ledge in Portland Harbor.
On September 8, 1869, coastal Maine incurred severe damage in a hurricane, which caused 30 shipwrecks along the coast, including the schooner Helen Eliza, which went aground off Peaks Island, with just one of the vessel's crew of 12 surviving.
[184] The Portland and Yarmouth Electric Railway was established in 1898, four years after its charter by Maine's state legislature, and eventually ran service between the municipalities on a half-hour schedule and underwrote the construction of the Underwood Spring Park casino resort in Falmouth to spur ridership.
"[202] Under the initial command of Major General Clarence Edwards, the Army's Northeastern Department[203] garrisoned coastal artillery batteries at existing forts on the Casco Bay shore and islands.
[208][209] With leisure spending dropping sharply during the war years, the Casco Bay and Harpswell Lines could not generate enough revenue to keep up with needed repairs for its ferries, and, facing liens on debt, declared bankruptcy in July 1919.
[210] Two years after creating a state harbor commission, in 1919 Maine's legislature authorized a $1.15 million bond issue to finance construction of a new wharf facility in Portland, in recognition of advancements in cargo handling at competing New England and Canadian ports.
[230] In the months leading up to the war declaration and afterward, U.S. Army Brigadier General Robert C. Garrett was commander of the Harbor Defenses of Portland based at Fort Williams in Cape Elizabeth.
An outer indicator loop ran from the southern tip of Staples Cove in Cape Elizabeth northeast to a point just east of Halfway Rock, then north to Land's End on Bailey Island.
[263] The tanker Northern Gulf struck West Cod Ledge off Two Lights State Park in November 1963, spilling at least 20,000 gallons of oil into waters at the outer edge of Casco Bay.
Oil-contaminated sand six inches deep was removed from West Beach on Long Island and transported to a landfill at Brunswick Naval Air Station, while contaminated straw used to absorb oil in the water, seaweed, and other debris was burned at a site in Gray.
[283] In October 2011, Portland completed $27 million in upgrades at Ocean Gateway International Marine Passenger Terminal that allowed for operators of large cruise ships to add the city to their ports of call.
[287] As of October 2024, the Maine Department of Marine Resources listed more than 50 active aquaculture site leases in Casco Bay managed by more than 30 operators, totaling about 220 acres for the nurture and harvest of oysters, clams, mussels, scallops and sugar kelp.
[355][356] Television and radio broadcaster Maine Public operates a Portland studio and affiliated website that reports frequently on news and issues affecting Casco Bay and its waterfront communities.
[358] Founded in 1983 and based in Rockland, the Island Institute publishes The Working Waterfront monthly which reports on the marine economy and environmental issues statewide, including in Casco Bay.