Nice work on the map.
I grew up not far from there by Western standards -- in Montana a bit north of Yellowstone Park -- and I'm pretty sure I've been on Little Sand Coulee Road, although I don't think we went north into the coulee where the branch road leads. So maybe I can give a little general information about the area.
Bureau of Land Management land is owned by the Federal government, which leases various rights to people or corporations that can make use of them. So ranchers will lease grazing rights, mining companies will lease mineral rights, etc. but in most cases the land itself remains accessible to the public. We were looking for fossils when we were there, but it's also popular with hunters, prospectors, and dirt bike/ATV enthusiasts. The roads will also be used by anybody who has leased rights from the BLM -- small miners working their claims, big mines with dumptrucks hauling out ore, ranchers checking on their cattle or sheep, lumber companies hauling out timber etc. I don't see any indication of big mining or lumber operations on the map, but there could be small mines, wildcat oil wells, etc.
This area gets almost no snow, as you can see from the photos, but it gets very cold.
Some of those fences might mark property lines, but for the most part they're to keep cattle from wandering. Unless the land is posted, which most ranchers don't bother with, you can't tell whether some of that might be private property.
If you look very closely at the map, you can kind of see a tiny line that seems to continue past the dead end, indicating that while the official road ends, you can still drive on. It might be a track made by offroad vehicles, or the road a rancher uses when feeding cattle in the winter, or a track up to a mine or lumber camp or something like that. There's another one that bends off to the right.
I have some more thoughts on that, but I want to think it through before I post anything.
