Cottonwood Canyon Road (BLM 400) is about a 50 mile gravel/dirt road in southern Utah that stretches between highway 89 at the south end and the town of Cannonville and highway 12 at the north. It’s a fairly tame road with a few patches of washboard. Most cars and any SUV should have no problem on it unless it’s wet. In that case 4wd would be required.
Highlights along this route include the cockscomb formation which is giant crack in the earth that runs along most of the route. Hackberry Canyon was also a nice surprise and there are many slot canyons and other hiking opportunities along the way. At the north end is Grovensor Arch which is an interesting formation.
I did this route in late May. I imagine it would be very hot in the summer months!
Get the Utah Benchmark Map I used for this trip below. These maps are super detailed, display 4wd roads, landmarks and more!