untamed stretches in the lower 48. Further south on a similar route (highway 12), Boulder, Utah was the LAST city in the united states to receive their mail by Mule.
It was the 1930s before Hell's Backbone was widened to allow for seasonal car traffic to reach Boulder. Highway 12 wouldn't come until later.
That stretch of Central Utah from the Swell all the way down to Powell (think hole in the rock) is unforgiving and beautiful.