Over the eons, the mighty Columbia River has worn this deep gash into the volcanic rock of the Cascade Mountain Range, nearly down to sea level. The last major period of erosion was occured during the Missoula Floods, which have been dated to have occured during the Ice Age. The most recent geological event was the Bonneville Slide in the 1700s, an event remembered in the local legends of the Native Americans as the Bridge of the Gods. Frequent rain nourishes a lush rain forest and replenishes the waters that cascade over the sheer basalt cliffs.
The western Gorge is dominated by conifer, big-leaf maple, cottonwood, Oregon ash, and vine maple. The eastern Gorge is home to Oregon white oak and big-leaf maple. Because of the wide range of elevation and precipitation in the Gorge, a diverse collection of endemic wildflowers thrives in the Gorge, from the temperate rain forest at Oneonta Gorge (with an average annual precipitation of 75 inches) to the Celilo grasslands (average annual precipitation 12 inches).
For over 31,000 years, the Columbia River Gorge has supported flourishing civilizations. Evidence of the Folsom and Marmes people, who crossed the Great Continental Divide from Asia, were found in archaeological digs. Excavations at Five Mile Rapids, a few miles east of The Dalles, show humans have occupied this ideal salmon-fishing site for more than 10,000 years.
The Columbia River Gorge is more than a beautiful natural wonder. It is also a critical transportation corridor, as well as one of the Pacific Northwest's favorite world-class outdoor playgrounds. Arguably the board-sailing capital of the world, the Gorge functions like a wind tunnel, generating 30-knot winds as pressure differentials in weather east and west of the Cascade Mountain Range find an outlet in the deep cut of the Gorge. The greatest concentration of waterfalls in the Pacific Northwest exists in the Columbia River Gorge -- there are 77 waterfalls on the Oregon side of the Gorge alone.
In November 1986, the United States Congress recognized the unique beauty of the Gorge by making it the nation's first National Scenic Area.