At the southern entrance to Wind River Canyon, a massive wall of earth and rock holds back one of central Wyoming’s largest bodies of water. Boysen Dam is easy to overlook while traveling between Shoshoni and Thermopolis, but it has played an essential role in the region for more than 70 years.
The dam controls flooding, generates electricity and stores water used by farms and communities downstream. It also created Boysen Reservoir, now a popular destination for fishing, boating, camping and exploring the rugged landscape at the edge of the Bighorn Basin.
A Dam Built for the Basin
The Wind River begins high in the mountains of western Wyoming and flows north toward the Owl Creek Mountains. After passing through Wind River Canyon, the same waterway becomes known as the Bighorn River.
Before Boysen Dam was constructed, the river’s flow could change dramatically with the seasons. Rapid mountain snowmelt sometimes produced damaging spring floods, while dry summers could leave the river running extremely low.
Federal officials began studying the possibility of building a large dam in the area during the early 20th century. The project was ultimately authorized in 1944 as part of the federal Pick-Sloan Missouri Basin Program, an enormous effort to develop irrigation, flood-control and hydroelectric projects throughout the Missouri River watershed.
According to the Bureau of Reclamation, construction of the current Boysen Dam took place between 1947 and 1952. The earth-and-rock-fill structure rises more than 200 feet and stretches approximately 1,100 feet across the river. Its hydroelectric power plant has a generating capacity of 15,000 kilowatts.
Today, the dam regulates Wind River flows for hydropower, irrigation, flood control, sediment management, wildlife and recreation. More than 60,000 acres of Wyoming farmland receive irrigation water from the Bighorn River downstream of the dam, according to the Bureau of Reclamation.
The First Boysen Dam
The current dam was not the first attempt to harness the river at Wind River Canyon.
In 1908, entrepreneur Asmus Boysen constructed a smaller concrete dam about a mile and a half downstream from the present structure. His project included a 710-kilowatt hydroelectric plant that supplied electricity to nearby communities and mining operations.
The location presented serious challenges. A major flood in 1923 raised the reservoir and inundated several miles of railroad track. Part of the dam was later removed to reduce the risk of future flooding, and power generation eventually ended.
Although Boysen’s original project was abandoned, his name remained attached to the site. Portions of the first dam can still be seen near the tunnels north of Lower Wind River Campground. Visitors interested in finding the location can consult information from Boysen State Park.
Creating Boysen Reservoir
The modern dam transformed the broad valley south of Wind River Canyon into Boysen Reservoir. The lake covers approximately 19,560 acres when full, extends about 20 miles and includes roughly 76 miles of shoreline.
Those dimensions make Boysen much more than a water-storage project. The reservoir and surrounding public lands form the heart of Boysen State Park, established in 1956.
The setting is distinctly Wyoming. Open sagebrush country surrounds the reservoir, while the Owl Creek Mountains rise near its northern end. Depending on the season, visitors may encounter everything from calm blue water and sandy beaches to powerful winds, winter ice and dramatic thunderstorms moving across the basin.
Fishing, Boating and Camping
Boysen Reservoir supports one of Wyoming’s most diverse fisheries. Anglers can pursue walleye, sauger, yellow perch, crappie, burbot—commonly called ling—and several species of trout. Largemouth bass, bluegill, mountain whitefish and other species are also present, according to Wyoming State Parks.
Fishing opportunities change throughout the year. Spring and fall can bring productive open-water fishing, summer attracts boaters and shoreline anglers, and winter turns the reservoir into a popular ice-fishing destination when conditions are safe.
Campgrounds and day-use areas are scattered around the reservoir and near the entrance to Wind River Canyon. Accommodations range from developed sites to simpler lakeside camping areas. Because individual facilities and water access can vary, visitors should review the current Boysen State Park camping information and make reservations before traveling.
Boaters should also remember that Wyoming’s wind can build quickly across the reservoir’s open water. Checking the forecast, carrying required safety equipment and remaining close to shore during changing conditions are important precautions.
A Gateway to Wind River Canyon
Boysen Dam also marks the beginning of one of Wyoming’s most impressive drives. From the dam, U.S. Highway 20 follows the river north through Wind River Canyon toward Thermopolis.
The canyon exposes hundreds of millions of years of geological history in its towering rock walls. Roadside signs identify many of the formations, allowing travelers to watch Wyoming’s geological record unfold as they drive.
This makes Boysen an excellent stop on a larger Bighorn Basin trip. Visitors can spend the morning fishing or exploring the reservoir, continue through Wind River Canyon and finish the day at Hot Springs State Park in Thermopolis.
Planning Your Visit
Boysen Dam is located on the Wind River near Shoshoni, approximately 17 miles south of Thermopolis along U.S. Highway 20. The reservoir and state park can be accessed from several roads and recreation areas surrounding the lake.
Before heading out, check:
- Current park and campground conditions
- Boat-ramp availability and reservoir levels
- Wyoming fishing-license requirements and regulations
- Weather and wind forecasts
- Any harmful cyanobacterial bloom or other recreational-use advisories
Check the latest information and any alerts at Boysen State Park alerts and follow all posted precautions around the water.
Boysen Dam may have been constructed as a practical piece of water infrastructure, but its impact reaches far beyond electricity and irrigation. It created a place where engineering, history, geology and outdoor recreation meet, right at the gateway to the Bighorn Basin.
Bighorn Basin Explorer 
Leave a comment