Across the U.S., Removing Old Dams Is Helping Fish Swim Home

In 1859, farmers in Billerica, Massachusetts, were fed up with a dam on the Concord River. The dam powered a factory, and the farmers said it flooded their fields and spoiled their hay. They hired a surveyor named Henry David Thoreau, who later became a famous author, to measure the river. Thoreau did not love surveying, but he had another reason to take the job. He disliked the dam because it blocked fish, such as American shad, from swimming upriver to lay their eggs. "Poor shad! Where is thy redress?" he had written years earlier. In the end the state let the dam stay.

Today the story is very different, Smithsonian magazine reports. Since 1912, more than 2,300 dams have been removed from U.S. waterways, most of them in the last 25 years. The movement peaked in 2024, when the nonprofit American Rivers counted removals that reconnected more than 2,500 miles of rivers and streams that had been cut into pieces.

The biggest project that year was on the Klamath River, where four aging dams that made electricity were taken down. That opened more than 400 miles of river for chinook salmon to lay their eggs in California and Oregon, and the fish returned so quickly that conservationists called it "magical." The largest removal before that took place on Washington State's Elwha River.

Dam removal is not just a western story. Most of the projects are in eastern states, where they are usually smaller and get less attention. In 2024, the Blake Higgins Dam came down in Vermont, the Edes Falls Dam was removed from Maine's Crooked River, and the Kimball Brook Dam disappeared from New Hampshire. Pennsylvania removed 27 old barriers that year, none taller than about 20 feet. Even the three-century-old Talbot Mills Dam that bothered Thoreau may soon be taken down.

Nathan Furey, a fish biologist at the University of New Hampshire, says the country is in a dam-removal renaissance, losing barriers faster than it builds them for the first time in history.