Stones aren't supposed to do that ..are they??? :'(
No, just a section line on a mountainside.
If I found this in Nebraska, my first guess would be a corner on a former Indian Reservation or Military Reserve.
At first glance I was reminded of a cemetery lot corner marker. But, in that case, it would be just one letter and that would indicate the first letter of the surname of the family who owned the lot. So that's not what you have found.
A better guess is that someone for some odd reason found or made the stone then went driving around looking for some weird place to stick it so that, someday, someone like you would find it and go nuts trying to determine the reason for it's existnence. The answer is "there is no reason".
There is ALWAYS a reason...
Sometimes it's just a dumb one, and those are the real head scratchers.
B-)
Loyal
I was thinking more like:
November 1, 1882
at at the section corner common to Sec.s 31 and 32 which is a marked stone as previously described by the Surveyor general, at 9:00 o'clock PM local mean time, I lay off 44^34" minutes on the vernier... and site a stoe marked with a "+" 5.00 chains distant to the east.....
on another note, it seems that i recall mil. reservation corners being marked "US".. or some such....
Any chance there is a vacated plat or townsite with a cemetery nearby?
Could be a center mark for a block old pioneer cemetery lots. Albeit the most sophisticated pioneer cemetery marker I have seen in a pioneer cemetery. But that might be a reasonable explanation for the ornate lettering.