At 5pm on July 18, 1814, the passengers aboard the Lubec-to-Eastport ferry witnessed a most unusual sight: a fleet of British warships, transports and storeships rounding the eastern end of Campobello Island and heading straight for Eastport.

The ferry’s skipper brought the little boat to a halt in mid-passage as the 11-vessel fleet came to anchor before the town. Britain and the United States had been at war for two years, but the conflict was unpopular in Massachusetts, which then ruled Maine, and it was widely assumed the British would leave New England alone. But now the ferry passengers watched as the British sent a boat ashore and, 30 minutes later, the stars and stripes were lowered at the town fort and replaced with the Union Jack.

The ferry’s journey was at an end. Their destination had just been annexed by a foreign power.

The British invasion of Maine, which left the eastern half of the territory under military occupation and the rest in constant threat of attack, is one of the watershed moments in our coast’s history. Indeed the invasion, and Boston’s shameful response to it, led directly to Maine becoming a state a few years later.

Before the invasion, Mainers were divided on whether to pursue independence from Massachusetts, which had ruled the territory since the 1650s. For the better part of a century, settlers in backcountry towns had been engaged in a violent insurgency against the schemes of Bay State land barons; they were more than happy to be rid of their overrule. But people in more established towns like Wiscasset, Portland, Eastport and Castine feared such a move would disrupt the coast’s economy, and squashed efforts at separation.

All that changed in the summer and fall of 1814, as British forces spread south, occupying Machias, Blue Hill, Belfast and Castine, looting Hampden and Bangor, and repeatedly attempting landings at Boothbay. By late summer, the people of Wiscasset expected their “village would be laid in ashes within twenty-four hours” as rumors spread that the British “were hovering upon our coast, or standing into our bays and rivers.” Banks moved their reserves to Portland, where militiamen rallied to defend the city.

“The whole District of Maine is threatened by the ravaging foe,” Washington’s leading newspaper reported, yet “scarcely a soldier of the U.S. troops is there to assist in repelling invasion, although thousands have been enlisted in that part of the country.”

Indeed, Maine was virtually defenseless as a result of Massachusetts’ policies. The ruling classes in Boston were deeply opposed to the war and openly sided with the British against the federal government in Washington. Boston bankers refused to loan President James Madison the money he needed to raise a proper federal army, yet advanced enormous sums to the British in Nova Scotia. As a result, Madison withdrew all federal troops to more loyal states, leaving Maine to be defended by “a few invalids…who were retained [in Maine] on account of their indispositions.”

After the invasion, Massachusetts Governor Caleb Strong called an emergency meeting of the state legislature. Maine representatives were shocked when their colleagues made it clear they “meant to say or do nothing” about the occupation of half the District of Maine. To make matters worse, when Madison tried to raise an army to liberate the area, Governor Strong not only refused to lend him money, his administration leaked the war plans to the Boston press, which published them in their entirety.

Had the war not ended when it did, eastern Maine might still be part of New Brunswick today. British officers had required inhabitants of Eastport and other towns to take an oath of loyalty to King George III and formally incorporated the easternmost settlements into the British Empire.

Even after word of peace reached New England in February 1815, British forces remained in Eastport, which they insisted had always been a part of New Brunswick, by dint of it being on an island. Eastport, a British commissioner once said, is British, “as much so as Northamptonshire.” U.S. Customs Houses complied, continuing to regard Eastport as a foreign city, while the town’s residents had to travel 15 miles to Dennysville to find the nearest U.S. post office. Several Eastport merchants fled across the water to Lubec, where they founded a sort-of trading-center-in-exile until the British finally withdrew in June 1718.

Maine was liberated, but the wartime damage to the District’s relationship with Massachusetts could not be undone. Those who had opposed the war and statehood in the past were shocked at how quick Boston was to abandon “the eastern territories” in time of war. “We have seen the Executive of the Commonwealth tamely submitting to the invasion of his territory without making one effort to expel the foe,” Bangor attorney Samuel Whiting exclaimed. “If Massachusetts won’t cooperate and the Federal government is unable to, then the crisis has arrived when the District of Maine ought to legislate for herself.”

After the war, the separation movement gained strength and, after several false starts, succeeded in pushing through a referendum for statehood in 1819. The following year, Maine was accepted into the Union, a separate political entity for the first time in 170 years thanks, ironically, to the British invasion.

Colin Woodard is the author of The Lobster Coast: Rebels, Rusticators, and the Struggle for a Forgotten Frontier. He lives in Portland and has a website: www.colinwoodard.com.