Corkscrew Bridge on Yellowstone Highway 

This is just east of Sylvan Pass, where my dad and uncles can be seen playing on the snow in 1940 home movie below. The fill from the new road probably obliterated the old alignment and features at the pass.
1940: • HC Toeppen 8mm Reel 01...
My dad is the youngest. The guy in the white hat is my uncle Don. He was flight manager for UAL at ORD in the 70's. The other uncle worked for Walgreen's for eons.
Aerial View: www.google.com...
If you scroll west a bit, you can see that the old road had intestinal switchbacks to gain elevation to reach the pass. The switchbacks are somewhat obscured by snow in the google view. If you look on historical aerials, the 1954 aerial has a clearer view.