The tallest dam in the United States isn’t Hoover or Oroville — it’s a mine tailings impoundment in Idaho. In fact, mine-waste structures in Appalachia dominate the top 10, with famous hydroelectric dams squeezed in between. This ranking pulls the 30 tallest dams in America directly from the US Army Corps of Engineers National Inventory of Dams.
—dams tracked
—high hazard
—poor / unsat condition
—high hazard & poor
Loading dams…
Hazard
Condition
Purpose
Explore all 92,469 US dams on the interactive US Dams Map, or read on for the full top-30 ranking.
Source: USACE National Inventory of Dams, ranked by NID Height.
Why Are So Many of the Tallest Dams Mine Tailings Impoundments?
At least 15 of the 30 tallest dams in America are mine tailings or slurry impoundments, most of them in the Appalachian coal basin (West Virginia, Kentucky) and a handful in the western metal-mining states (Idaho, Montana). These aren’t traditional water-storage dams — they’re engineered structures built up over decades to contain the fine-grained waste left over after ore is processed.
The reason they reach such heights is cumulative: the dam wall is raised as the impoundment fills, sometimes for 40 or 50 years. Their safety profile is different too — several in the top 30 carry “Not Rated” or “Not Available” condition assessments, compared to routine Satisfactory/Fair/Poor ratings for conventional hydroelectric dams. The classification details, and what the condition ratings actually mean, are covered in Dam Hazard Classifications Explained.
The Tallest Conventional Dams in the US
If you set aside tailings impoundments and water-supply dams like Kentucky’s Abner Fork and Half Mile, the “famous” tallest-dams list runs:
Oroville — 770 ft — California — Flood Risk Reduction — 1968
Hoover Dam — 730 ft — Nevada — Hydroelectric — 1935
Dworshak Dam — 717 ft — Idaho — Flood Risk Reduction — 1973
Glen Canyon Dam — 710 ft — Arizona — Hydroelectric — 1963
New Bullards Bar — 645 ft — California — Hydroelectric — 1970
New Melones Dam — 625 ft — California — Hydroelectric — 1979
Mossyrock — 606 ft — Washington — Hydroelectric — 1968
Shasta Dam — 602 ft — California — Hydroelectric — 1945
Don Pedro Main — 585 ft — California — Hydroelectric — 1971
Hungry Horse Dam — 564 ft — Montana — Flood Risk Reduction — 1953
California alone holds five of the top 10 conventional dams by height — the legacy of mid-20th-century federal water and power infrastructure built to support the state’s expanding cities and Central Valley agriculture.
Where the Tall Dams Cluster
The states with the most dams in the top 30 are an unusual mix:
California — 7 dams (Oroville, New Bullards Bar, New Melones, Shasta, Don Pedro Main, Seven Oaks, Trinity). The west coast water-and-power empire.
West Virginia — 6 dams, all coal-slurry impoundments built up over decades.
Kentucky — 5 dams, four of them mine-related and one extreme water-supply structure (Abner Fork).
Washington — 3 dams — Mossyrock, Grand Coulee, and Ross, all on or near the Columbia River system.
Montana — 3 dams — one tailings (Yankee Doodle) and two federal dams (Hungry Horse, Yellowtail).
Idaho — 2 dams — the tallest structure in the country (Thompson Mtis) and Dworshak.
Frequently Asked Questions
What is the tallest dam in the United States?
The tallest structure classified as a dam in the National Inventory of Dams is the Thompson Mtis tailings dam in Idaho (789 ft). Among conventional water-storage dams, Oroville Dam in California (770 ft) is the tallest.
Is Hoover Dam the tallest dam in America?
No. At 730 feet, Hoover Dam is the 5th-tallest structure in the National Inventory of Dams and the 2nd-tallest conventional hydroelectric dam (behind Oroville). It was the tallest in the world when completed in 1935.
How is dam height measured?
The National Inventory of Dams uses “NID Height,” defined as the maximum of the dam’s hydraulic height, structural height, or dam height — whichever is greatest. It’s the measurement used for federal safety regulations and ranking.
What is the tallest dam in the world?
The world’s tallest dam is Jinping-I Dam in China at 1,001 feet (305 m). The tallest US dam (Thompson Mtis, 789 ft) would rank around 15th globally.
I'm Daniel O'Donohue, the voice and creator behind The MapScaping Podcast ( A podcast for the geospatial community ). With a professional background as a geospatial specialist, I've spent years harnessing the power of spatial to unravel the complexities of our world, one layer at a time.
