[6] The geologic history of the rocks of Hells Canyon began 300 million years ago with an arc of volcanoes that emerged from the waters of the Pacific Ocean.

Between 130 and 17 million years ago, the ocean plate carrying the volcanoes collided with and became part of the North American continent.

A period of volcanic activity followed, and much of the area was covered with floods of basalt lava, which smoothed the topography into a high plateau.

Significant canyon-shaping events occurred as recently as 15,000 years ago during a massive outburst flood from Glacial Lake Bonneville in Utah.

[11] In 1955, the commission issued a license to the Idaho Power Company to build a three-dam complex in the canyon: The three dams have a combined generating capacity of 1,167 megawatts (MW) of electricity.

[12] The complex, which provides about 70 percent of Idaho's hydroelectricity, blocks migration of salmon and other anadromous fish upstream of Hells Canyon Dam.

[14][15] At the end of that year, President Gerald Ford signed legislation to create the Hells Canyon National Recreation Area and the projects were terminated.

[20] Activities in Hells Canyon include fishing, jet boat tours, hunting, hiking, camping, and whitewater sports (mainly rafting and kayaking).

The Snake River is home to numerous fish species, an abundance of class I-IV rapids (some of the largest in the Pacific Northwest), diverse wildlife and miles of systems.

There are three roads that lead to the Snake River and they are located between Hells Canyon Dam and the Oregon-Washington state line.

[23] The road crosses the dam and continues another mile to the Hells Canyon Visitor Center on the Oregon side.

[25] On the canyon rims, viewpoints accessible by road include Hat Point and Buckhorn in Oregon and Heavens Gate in Idaho.