Whether you’re road-tripping or prepping yourself for your dream spot on Jeopardy!, it’s essential to get familiar with the nation’s most monumental dams.

But to find those hulking structures—blockades against water made of earth and concrete— you’ll need to fix your gaze west of the Rockies. When engineers seek to block up rivers to create hydroelectricity or to simply control water flow, they’ll often look to the mountainous stretches of Arizona, California, Washington, and Montana.

Inside the mountainous ravines of the U.S., there are earthen walls, concrete ones, and sometimes even barricades made out of steel, all working to plug up rivers. Some have even stood for over 100 years, before the land they were on was even part of the Union.

1Theodore Roosevelt Dam: Roosevelt, Arizona
theodore roosevelt dam at theodore roosevelt lake, az

Once known as the world’s largest masonry dam—a title now bestowed upon the Nagarjuna Sagar Dam in India—the Theodore Roosevelt Dam was originally constructed between 1905 and 1911. The premise was simple: halt the wayward flow of the Salt River to irrigate the harsh Arizona desert, making it more amenable to farming.

When it was first constructed, the dam made use of a Greco-Roman style that favored large, irregularly shaped blocks. However, following a $430 million renovation project in 1996, the dam was covered in new concrete, masking the masonry.

The structure is named for President Theodore Roosevelt, who was instrumental in passing the Federal Reclamation Act of 1902, which funded irrigation projects in the West. At completion, the resulting reservoir–Theodore Roosevelt Lake—came in at 526,875 acre-feet of water, making it the largest manmade lake at the time.

2Oroville Dam: Feather River, California

Forget heavy concrete for a moment—the tallest dam in the U.S. doesn’t need it. About 70 miles north of Sacramento along the Feather River in the Sierra-Nevada foothills, this earthfill dam rises 770 feet tall and, at the base, has a reach of three quarters of a mile.

This mound of earth stops up the Lake Oroville reservoir, which offers drinking water, water-based recreation, and hydroelectric power while mitigating flood damage. It was officially dedicated in 1968, seven years since the start of construction—with one giant train wreck during construction that halted all progress for a week. Since then, the Oroville has stood as the country’s tallest dam for more than 50 years.

3Hoover Dam: Colorado River, Arizona/Nevada

The superlatives fly when it comes to the Hoover Dam. Built between 1931 and 1935, the Art Deco-detailed dam was easily the most expensive engineering project in the U.S. at the time and became the tallest dam in the country at 726 feet tall. Still the second-tallest dam overall and the tallest concrete dam, it required 91.8 billion cubic feet of concrete to create the arch-gravity dam with a 600-foot-wide base, weighing 6.6 million tons in total.

The Hoover Dam holds back the Colorado River and straddles the border between Arizona and Nevada near Boulder City, Nevada, a town originally created for the project’s workers. Behind Hoover, Lake Mead fills as the largest manmade reservoir in the country.

4Grand Coulee Dam: Spokane, Washington

The Grand Coulee Dam may not be the tallest at 550 feet, but the seriousness of this 1942-built dam outside of Spokane, Washington comes from its sheer size. With over 12 million cubic yards of concrete, the Ground Coulee Dam spans the Columbia River for nearly a full mile, backing up Franklin D. Roosevelt Lake reservoir nearly to Canada.

Depending on your preferred analogy, the Grand Coulee Dam contains enough concrete to build a highway from Miami to Seattle or a sidewalk around the Equator—twice. But the dam doesn’t just sit there. With 21 billion kilowatt-hours of electricity annually, Grand Coulee creates the most hydroelectric power of any dam in the U.S.

5Dworshak Dam: Orofino, Idaho

It took roughly seven years to build what would become the third-tallest dam in the nation and the tallest straight-axis (not curved) concrete gravity dam in the Western Hemisphere. Since 1973, Dworshak has sat a few miles outside of Orofino, Idaho, blocking up the Clearwater River and creating the Dworshak Reservoir.

Despite its impressiveness, the 717-foot tall dam was never a popular project. Dworshak has been saddled with controversy—1990s-era expansion approvals were rescinded for disrupting the natural wildlife of the area.

6Fort Peck Dam: Glasgow, Montana

Forget the concrete and don’t worry about the height. At just 250 feet tall, the impressiveness of the Missouri River’s highest dam comes in its breadth. At over 21,000 feet in length and with a base width of 3,500 feet, Fort Peck is the largest hydraulically filled dam in the world.

U.S. Army Corps of Engineers crews created the New Deal-era dam by pumping sediment from the bottom of the Missouri River and mixing it with rock and natural materials to form the dam in 1940. Fort Peck Lake rests behind the dam, and hydroelectric generation started in 1943, complete with an Art Deco spillway. It can pump out a staggering 250,000 cubic feet of water per second.

7Glen Canyon Dam: Page, Arizona


At 710 feet tall, this concrete arch-gravity dam near Page, Arizona fills a canyon-heavy region on the upper Colorado River with water. Under construction from 1956 to 1966, the dam forms Lake Powell behind it, the second-largest manmade reservoir in the U.S.

Conceived of before the Hoover Dam, but built later, Glen Canyon helps manage water distribution in the river’s basin and, along with hydroelectricity generation, can help hold onto runoff for lean water years while ensuring fewer droughts for those downstream.

During the dam’s construction, the Glen Canyon Bridge, a steel arch bridge spanning the river’s canyon, became the highest arch bridge in the world at the time of its 1959 completion.


8Ashfork-Bainbridge Steel Dam, Johnson Canyon, Arizona

Almost everything about the Ashfork-Bainbridge Steel Dam is different than a typical dam in the West. Not only is it one of only two major dams in the nation using steel—the first of the two—this 1898-completed structure was not meant to generate hydroelectricity like its counterparts.

Owned by the Atchison, Topeka, and Santa Fe Railway, the steel moved water from Johnson Canyon via piping into the town of Ash Fork, supplying a water stop for steam locomotives. The dam contains 24 curved steel plates fabricated by the Wisconsin Bridge and Iron Company and runs 184 feet long and 46 feet high. It’s been holding back water since before Arizona, the state where it resides, was officially part of the Union.