Black and white photograph of a dam, possibly the Hetch Hetchy. A road is carved into the mountainside next to the dam.

Shoshone Dam near the entrance to Yellowstone Park, Wyoming.

Shoshone Dam near the entrance to Yellowstone Park, Wyoming.

Power house below Shoshone Dam, Wyoming.

Canyon below Shoshone Dam, Wyoming.

Dam on the Onion River in Wisconsin.

Dam on the Onion River in Wisconsin.

Dam on Onion River in Wisconsin.

Little Dell dam in Parley's Canyon is a source for Salt Lake City water supply.

Norris Dam on the Clinch River in Tennessee.

Norris Dam on the Clinch River in Tennessee.

Norris Dam on the Clinch River in Tennessee.