The last two coal-fired power plants in New England are set to close by 2025 and 2028, ending the use of a fossil fuel that supplied electricity to the region for more than 50 years.

The decision to close the Merrimack and Schiller stations, both in New Hampshire, makes New England the second region in the country, after the Pacific Northwest, to stop burning coal.

Environmentalists waged a five-year legal battle against the New Hampshire plants, saying that the owner had discharged warm water from steam turbines into a nearby river without cooling it first to match the natural temperature.

In a settlement reached on Wednesday with the Sierra Club and the Conservative Law Foundation, Granite Shore Power, the owner of the plants, agreed that Schiller would not run after Dec. 31, 2025 and that Merrimack would cease operations no later than June 2028.

“This announcement is the culmination of years of persistence and dedication from so many people across New England,” said Gina McCarthy, a former national climate adviser to President Biden and former administrator of the Environmental Protection Agency during the Obama administration who is now a senior adviser at Bloomberg Philanthropies, which supports efforts to phase out coal.

“I’m wicked proud to live in New England today and be here,” Ms. McCarthy said. “Every day, we’re showing the rest of the country that we will secure our clean energy future without compromising.”