For the past 125 years or so, outsiders have been coming to our coast precisely because of its unspoiled, under-populated, and surprisingly un-industrialized and undeveloped landscape. Our coast—unique to the seaboard of the northeastern U.S.—has been a backwater, a place people come to get away from it all, rather than in pursuit of economic opportunity.

But it hasn’t always been thus. In the first few decades after statehood in 1820, the Maine coast was thriving and the state had a place in the national economy more significant than at any time before or since. At a time when the nation’s commerce still moved north to south in the hulls of wooden sailing vessels, Maine was at the heart of the action. We produced, crewed and owned many of those ships, and we often filled them with our coast’s resources, which were then in demand in the rapidly expanding cities of the eastern U.S.—resources like granite (for building and street paving), ice (to refrigerate in the subtropics in a time before refrigeration) or salt fish (one of the few forms of animal protein available to laborers and slaves). Portland was emerging as a potential rival to the port of Boston, while elegant captain’s mansions sprang up around busy harbors from Bath and Wiscasset to Searsport and Castine.

And it wasn’t just economics. By 1860, Maine had emerged as an influential force in national politics, with a rapidly expanding population, and six seats in the U.S. Congress—more than Florida, Texas and California combined. Mainer Hannibal Hamlin was Vice President, and Portland’s William Pitt Fessenden was one of the most powerful U.S. Senators. Our early elections had a disproportionate influence on political campaigns, much as the New Hampshire primaries do today, informing the saying “As Maine Goes, So Goes the Nation.”

So what happened? A cataclysmic event 150 years ago this year: the U.S. Civil War.

The Maine coast was far removed from the war zone, of course, but it arguably would suffer more than almost any other part of the North. Over 9,300 Maine soldiers and sailors would die—and 9,000 more would be injured—on the fields of Pennsylvania and Dixie, the second highest casualty rate in the North. The First Maine Heavy Infantry Artillery experienced the largest single-day casualty rate of any Federal unit in the war, with 632 of 950 men killed, wounded, or missing at Petersburg.

Those at home watched the state’s coastal trade and most of its once-thriving textile industry collapse, cut off from southern markets and sources of cotton. The fishing fleet contracted as the cost of everything from insurance to canvas exploded. Farmers, cut off from seaborne markets, were forced to abandon their farms, and many would flee to the south and west where, on the advice of soldiers’ letters, they could expect to find better soils and transportation links. Lumbermen decamped for the forests of the Great Lakes and, not long thereafter, the Pacific Northwest, where entire lumbering towns were settled almost exclusively by people from the Machias area.

The wartime clash between the ironclads Monitor and Merrimac was a death knell for the Age of Sail, and with it our coast’s shipbuilding and shipping sectors. To make matters worse, after the war the commerce of the nation began moving east to west on the expanding railroads, which were slow to come up the coast on account of the many rivers and estuaries and the shortage of people. Being on the way to New Brunswick wasn’t a selling point with the railroad barons.

As a result, Maine—and the coast in particular—suffered a profound demographic reversal. Whereas the state’s population had grown by more than eight percent between 1850 and 1860, it actually fell between 1860 and 1870. In the century and a half since, it has merely doubled, while the country at large has seen a ten-fold increase in population, relegating Maine to the sidelines of national politics. Abandoned, weather-beaten farms and fields of wildflowers would attract the early summer people who began showing up thereafter—shades of Andrew Wyeth—but to locals they were monuments to the region’s economic collapse. Indeed, parts of the coast still haven’t recovered, 150 years later.

It was a war that saved the Union, but not the coast of Maine.

Colin Woodard is the author of The Lobster Coast, The Republic of Pirates, Ocean’s End and the forthcoming American Nations: A History of the Eleven Rival Regional Cultures of North America (Viking, Sept. 29.)