This is the Boysen Dam at the southern end of Wind River Canyon.
The sign below says:
WIND RIVER CANYONBoysen Dam, completed in 1951, marks the southern margin of the east-west trending Owl Creek Mountains and the Wind River Canyon. Drained by the north flowing Wind River, the canyon is 14 miles long, 1.3 - 2 miles wide and 2,400 feet deep where it crosses the axis of the mountain range, north of here. Steep canyon walls display rocks of the Precambrian and Paleozoic eras ranging in age from several billion to 235 million years. The Wind River originally flowed across flat terrain beneath which lay the buried Owl Creek Mountains. These mountains formed 50 million years ago, as an upward fold in the earth's crust, and were subsequently covered by younger sediment. About 4 million years ago a broad regional uplift of the earth's crust resulted in the incision of the wind river's channel onto the rising crust, creating the canyon which cuts across the Owl Creek Mountains at a right angle. Rivers usually flow around or parallel to mountains, rather than across them. Sediment covering the Owl Creek Mountains was removed via erosion, resulting in development of the landscape you now view. The process continues.Portions of the Canyon highway follow an ancient trail used by Native Americans, early fur trappers, traders, and U.S. Military expeditions. Native Americans, particularly the Shoshone, used this trail to reach the hot springs in present-day Thermopolis. William Ashley, "general" of the fur trade, floated a valuable cargo of pelts through the Canyon in 1825 on his way back to St. Louis. The Canyon was also a well known escape route for Native American warriors in the late 1800s. Wind River Canyon is sacred to contemporary Native American tribes in the region.
BOYSEN DAM and RESERVOIR TODAYIn 1952, dignitaries dedicated a new dam built by the Bureau of Reclamation, one and half miles upstream from Asmus Boysen's historic dam.Construction began with blasting a tunnel to divert the river and included relocation of both the highway and the railroad. The new earth filled structure is 1,100 feet long and 230 feet high. The powerplant, located near the spillway, provides power to northwest Wyoming and ties in with other federal power lines.Boysen dam also serves as a flood control barrier for the Big Horn Basin and provides irrigation for over 100,000 acres of farm land.Today, Boysen is best known for the State Park that surrounds the reservoir and provides recreational opportunities for thousands of visitors to camp, fish, boat and water-ski.It all began with a dream and desire on the part of Asmus Boysen, the man responsible for the dam's design and creation in the early 1900s. The result was a dam, a reservoir and park that are all an integral part of life in Central Wyoming.
GEOLOGY of the WIND RIVER CANYONThe Wind River Canyon provides a unique slice through geologic time. While driving through the canyon, you can see rocks that were deposited when life was beginning and when Wyoming was covered by a sea with tropical climate similar to the Gulf of Mexico today.Over the last 100 million years, the Owl Creek Mountains were uplifted, folded, faulted and then eroded by the Wind River to form this spectacular canyon. Because the rocks were folded and tilted from a horizontal to a slight angle toward the north, you will drive past geologic formations from Precambrian (nearly 2.9 billion years old) to Triassic (over 200 million years old) in age, spanning a time period of over 2.7 billion years. Rock types including granite, basalt, metamorphosed volcanic rocks (amphibolite and schist), limestone, dolomite, sandstone, siltstone and shale are exposed in these outcrops.The formations cropping out in the canyon are marked by brown informational signs that list the period, the name of the formation and its age.
For a satellite view of the dam, click here.
Below is the railroad bridge which crosses the Wind River. The tunnel on the left is the route the railroad used to take before Boysen Dam was built.
The pile of rocks at the entrance of the tunnel is from a cave-in. You can see the light coming through from above. Be careful if you enter this tunnel because we came within a foot of more falling rocks.
Returning north to Thermopolis, we stopped at one of the turnouts (about a mile north of the three highway tunnels) to take these last two photographs. The first looks south toward the dam, and the second looks north. If you want a satellite view of this location, click here.