The Rivers Where Salmon Returned After The Dams Came Down
More than 2,200 dams have come down across the United States since record-keeping began in 1912, and the pace has never been faster than in the last decade. The results have settled an argument that used to be genuinely open: nobody was certain whether salmon would find habitat their ancestors had not reached in a century, or how long it would take. The answer turned out to be weeks, not generations. On the Klamath, fish were spawning above a removed dam site within about three weeks of the river being reconnected, in water that had been blocked since the early 1960s. That speed has changed how biologists talk about restoration and has also produced a few honest failures worth noting alongside the wins.
These are the rivers with the clearest before-and-after records, starting with the biggest.
Klamath River, California And Oregon
Four dams along the California-Oregon border represent the largest dam removal project in U.S. history and the most extensive salmon restoration effort ever undertaken. Copco 2 was dismantled in 2023, while JC Boyle, Copco 1, and Iron Gate were mostly removed in 2024, often overlapping rather than sequentially, with the last sections of Iron Gate removed by October that year.
Volitional fish passage resumed on September 26, 2024. On October 1, an adult Pacific lamprey was recorded passing through Jenny Creek's counting station. By October 15, biologists observed fall Chinook spawning in Jenny Creek, 4.3 river miles upstream of the old Iron Gate site. The following day, Chinook were also seen at a tributary mouth in Oregon, 230 miles from the ocean and upstream of all four former dams. California's wildlife agency noted these are the first anadromous fish in California tributaries above Iron Gate since 1961.
Sonar recorded over 9,600 fish crossing the old threshold that first fall, including approximately 7,700 Chinook. The next year showed improvement. In fall 2025, about 39,860 adult fall-run Chinook spawned naturally in the Klamath and its tributaries, surpassing the preseason forecast of 19,417 by 205%. At the Iron Gate site, monitors observed 11,722 adults. The count of jacks, or early-returning young males, increased from 7,085 in 2024 to 18,574 in 2025, which typically indicates a strong upcoming adult run.
Here is the necessary caveat. That 2025 run was still only about 61 percent of the 48-year long-term average. The three-year average escapement moved the stock from "overfished" to "rebuilding," which matters, but the river is recovering rather than recovered.
Elwha River, Washington
Before the Klamath, the Elwha in Washington served as the reference point. In the early 1900s, two dams were built: the 105-foot Elwha Dam and the 210-foot Glines Canyon Dam, both without fish ladders. Together, they blocked more than 90 percent of the watershed from anadromous fish. In 1992, Congress enacted the Elwha River Ecosystem and Fisheries Restoration Act. The dam removal took place from September 2011 to October 2014, restoring access to over 70 miles of habitat.
The recolonization data is the most comprehensive available. Within two and a half years of removing the lower dam, eight anadromous species were observed above the old site, including Chinook, coho, sockeye, pink, chum, winter and summer steelhead, and Pacific lamprey. After five years, all except chum had also moved past the upper Glines Canyon site. Adult Chinook expanded their range by about 30 miles, and summer steelhead by nearly 40 miles.
The key evidence convincing skeptics was that Chinook densities in some recently opened middle-river sections surpassed the highest levels previously recorded in the lower river before removal. Adult Chinook returns reached their peak since the late 1980s, with over 7,600 estimated in 2019. Additionally, in fall 2023, the Lower Elwha Klallam Tribe conducted a ceremonial and subsistence coho fishery for the first time since the removal.
It was not painless. A prolonged period of extreme turbidity in spring 2013 killed thousands of juvenile hatchery Chinook that were stranded as flows dropped. Sediment released by dam removal is a real short-term cost, and biologists expect the river to need decades to reach a steady state.
White Salmon River, Washington
The 125-foot Condit Dam was removed from the White Salmon River in 2011 using a notable method. Instead of dismantling it gradually, the crews blew a hole in its base, causing the reservoir to drain within hours.
The White Salmon, a tributary of the Columbia River, saw salmon and steelhead almost immediately return after the reach was reopened. While not as prominent as the Klamath or the Elwha, it stands as one of the clearest examples that fish don't require human intervention to return; given the chance, they will naturally find their way.
Kennebec River, Maine
The Kennebec River was the site of the initial action. On July 1, 1999, excavators began removing the Edwards Dam in Augusta, with about a thousand spectators on the banks, including Interior Secretary Bruce Babbitt and Governor Angus King. The dam, measuring 917 feet in length and 24 feet in height, was constructed of timber-crib and concrete. It had been impeding 17 miles of river since 1837.
What made it historic was not its size. It was the first time the federal government ordered a working hydroelectric dam torn down against its owner's wishes to protect the river.
The response was swift and steadily grew. Within weeks, striped bass began hunting above the old dam site. After the Fort Halifax Dam on the Sebasticook tributary was built in 2008, the alewife run increased dramatically. The lower Kennebec now hosts North America's largest river herring run, with annual estimates of three to five million fish, and over 36 million alewives have passed Benton Falls since 2009. Additionally, shad, sturgeon, and American eels returned alongside them.
Penobscot River, Maine
The Penobscot stands out as the straightforward and most educational example on this list. Over a 16-year period, approximately $60 million was invested to remove the Great Works Dam in 2012 and the Veazie Dam in 2013. Subsequently, a stream-like bypass was constructed around Howland, restoring access to about 1,000 miles of watershed.
Alewives reacted similarly on the Kennebec, with two to three million now migrating upriver. Alongside them, bald eagle populations increased because alewives serve as prey.
Atlantic salmon did not. They remain perilously close to extinction in the United States, surviving in Maine and nowhere else in New England. Returns have improved from record lows without approaching a self-sustaining run. The reason is instructive: Atlantic salmon need headwaters, and headwaters are still behind dams. A 2023 paper in Frontiers in Ecology and Evolution laid out seven separate ways dams keep burdening migratory fish even after a restoration project, and state biologists estimate only about half of salmon find the fish lift at the lowest Kennebec dam. Apply a rate like that across four barriers and barely one fish in sixteen reaches the top.
What The Pattern Actually Shows
Three things hold across every river here.
Fish arrive faster than anyone predicted. Not one of these recoveries required decades to show a first signal, and most produced spawning fish in the first season. Ecologists sometimes call this ecological memory, the idea that a system retains the capacity to function long after it stops functioning.
Forage fish, like Alewives and river herring, recover quickly within three or four spawning cycles, while larger migratory species such as Chinook take more time to recover. Atlantic salmon might not recover at all.
Partial removal leads to only partial results. The Klamath case succeeded because all four dams were removed. In contrast, the Penobscot's salmon remain trapped because the dams upstream are still in place.
What It Does Not Prove
None of this suggests that dam removal is a universal solution. The successful projects typically involved outdated or low-value structures, many of which were privately owned, some illegal or unlicensed, and in the case of the Elwha, one located within a national park. There are no plans to remove Bonneville.
The record clearly shows a narrower and more practical understanding. When a barrier appears in a river with fish downstream and habitat upstream, the fish will naturally find the upstream habitat quickly, without needing to be transported. This was uncertain in 1999 but is now well-established.
