Originally, the old Columbia Gorge Highway crossed Oneonta Creek and bored through the neighboring cliff in a tunnel. From the highway bridge at the mouth of the gorge,look for the old tunnel entrance on the cliff to the left, now filled with rubble.

Oneonta Creek has cut down through a series of Columbia River Basalt lava layers by following a fault line - a crack in the ground that aligns this gorge as straight as an arrow.