Few visitors know this road once ran through two tunnels. Both were removed within about four years of use, and only the slopes crowding the highway hint at the spot. Nearby stands Toadstool Rock, a Sharps Formation boulder perched on softer Brule mudstone, and the climb over Norbeck Pass.
Nothing marks it, but less than a mile back you came through where a tunnel stood. This road once had two, and this rock is too soft to trust overhead. Keep your eyes on the right side now for Toadstool Rock. It's an enormous boulder of hard river sandstone balanced on a stem of mudstone that's wearing away beneath it. That's a hoodoo. The state cut the tunnels into the formations in the early nineteen thirties. The lower one sat near the foot of Norbeck Pass. The upper one, near Pinnacles, was one hundred seventy-five feet long and sixteen wide. They were too narrow, and each saw only about four years of traffic. By June of nineteen forty, relief crews had erased them both. The slopes still hug the road where they were. One highway engineer saw the trouble coming. This road ran through one of the world's most fantastic examples of erosion, he said. So maintenance would be neither simple nor easy. Norbeck Pass is the steep hill where the lower prairie gives way to the upper.
Photo: NPS Photo / Serena Rosales, public domain · Public domain