Hells Canyon is a ten-mile wide canyon located along the border of eastern Oregon and western Idaho in the United States. It is North America's deepest river gorge at 7,993 feet (2436 m) and the most important feature of Hells Canyon National Recreation Area.

The canyon was carved by the waters of the Snake River, which plunges more than a mile below the canyon's west rim on the Oregon side and 8,000 feet below the peaks of Idaho's Seven Devils Mountains range to the east. Most of the area is inaccessible by road.

Artifacts from prehistoric inhabitants as well as the ruins of early 19th century miners and settlers are visible.

History

The earliest known settlers in Hells Canyon were the Nez Percé tribe. Others tribes visiting the area were the Shoshone-Bannock, northern Paiute and Cayuse Indians. The mild winters, and ample plant and wildlife attracted human habitation. Pictographs and petroglyphs on the walls of the canyon are a record of the Indian settlements.

In 1806, three members of the Lewis and Clark Expedition entered Hells Canyon along the Salmon River. They turned back without seeing the canyon. It was not until 1811 that the Wilson Price Hunt expedition explored Hells Canyon while seeking a shortcut to the Columbia River. Hunger and cold forced them to turn back, as did many explorers who were defeated by the canyon's inaccessibility. There remains no evidence in the canyon of their attempts; their expedition journals are the only documentation.

The early miners were next to follow. In the 1860s gold was discovered in river bars near present-day Hells Canyon National Recreation Area, and miners soon penetrated Hells Canyon. Gold mining was not profitable here. Evidence of their endeavors remains visible along the corridor of the Snake River. Later efforts concentrated on hard-rock mining, requiring complex facilities. Evidence of these developments is visible today, especially near the mouth of the Imnaha River.

In the 1880s there was a short-lived homesteading boom, but the weather was too severe for farming and settlers soon gave up. Some ranchers still remain today operating within the boundaries of the National Recreation Area.

Geological history

The geologic history of the rocks of Hells Canyon begins 300 million years ago with an arc of volcanoes that emerged from the waters of the Pacific Ocean. Over millions of years, the volcanoes subsided and limestone built up on the underwater platforms. The basins between them were filled with sedimentary rock. 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. The Snake River began carving Hells Canyon out of the plateau about 6 million years ago. Significant canyon-shaping events occurred as recently as 15,000 years ago during a massive outburst flood from Glacial Lake Bonneville in Utah.

credited to wikipedia