Cascade Rapids

This Great Shute or falls is about 1/2 a mile, with the water of this great river Compressed within the Space of 150 paces in which there is great numbers of both large and Small rocks, water passing with great velocity forming & boiling in a most horriable manner, with a fall of about 20 feet.
-William Clark, October 31, 1805

Sometime around 500 years ago, steeply angled layers of basalt on Table Mountain just north of the present Bonneville Dam site slid into the Columbia River. The natural dam that resulted from the landslide backed up the river for 70 miles—as far as the John Day River. It is widely considered to be the source of the Native American legend of the 'Bridge of the Gods.'

Eventually, the lake breached the dam, sending a wall of water surging down the Columbia River Gorge. Left in the wake of this cataclysmic series of events was William Clarke’s Great Shute, or the Cascade Rapids. The Corps of Discovery was forced to portage around the rapids and received minor damage to three canoes by lowering them over the rocks with poles.

The Cascade Rapids continued to be an obstacle for explorers and travelers for decades. Pioneers on the Oregon Trail who built rafts or hired guides to navigate the Gorge were faced with a difficult choice between risking the rapids or making the arduous portage. Not until the Cascade Locks were completed in 1896 was an easier passage available.

The Cascade Rapids were drowned in 1953 with the completion of the Bonneville Dam. The only evidence of the rapids today is a navigational lock at Cascade Locks. The Cascade Locks Historical Museum tells the story of the rapids, the portage, and river navigation in general.