Over its 13-million-year life span, Snake River, which neatly straddles the border between Oregon and Idaho, has carved out the deepest river gorge in North America – yes, at 8000ft from highest peak to river, it's deeper even than the Grand Canyon (though not nearly as dramatic). Originating in Yellowstone National Park and ending at the Columbia River near Pasco, WA, the river runs more than 1000 miles in total.
The prehistoric people who dwelt along Hells Canyon left pictographs, petroglyphs and pit dwellings. The Shoshone and Nez Percé tribes battled for dominance along this stretch of the Snake, with the Nez Percé winning out. Relics of the mining era, from the 1860s to the 1920s, are also found throughout the canyon, and tumbledown shacks remain from the unlikely settlement attempts of turn-of-the-century homesteaders.