As much as I like the backcountry, you could be pressing my limits for Rockdocking locations! We have driven past the Henry Mountains many times and kept going. These were the last explored mountains in the Continental USA by the US Geological Survey done by a geologist G. K Gilbert. Nobody else wanted to tackle it, but mostly because it was a volcanic mountain range and economic minerals were probably not to be found there. There is a book by Gilbert in 1877 titled "Report on the Geology of the Henry Mountains". Another paper is more common to find by Charles B. Hunt titled "Geology and Geography of the Henry Mountains Region, Utah", 1953
and includes geologic maps and details...
It might be a good place to visit in the Spring, Fall or Winter, but it always looks HOT to us when we pass there during these seasons, as well. A quote from USGS geologist C. B. Hunt... "It (Henry Mountains) has not been penetrated by modern methods of transportation (rubber wheeled vehicles, trailers, etc.) and thus it persists as a roadless frontier." This was a 1953
If you can talk your buddies into going, I would like to know how you fared. It could be easier getting in there than out... Some one in Hanksville, Utah might have an access road that will get you into there. Since we like looking for agates or anything shiny, this area looked like paying high dues to get into the area and praying to make our way back out!