Nobody knows what they are for. They apparently are pre-Columbian but
They run from Canada to Mexico, I have read, along the eastern front of the Rockies.
This is on state land east of Melville Montana just about a mile from the closest public road. I was out there to see what was there and maybe find an antelope or maybe a coolee with some trees with a Mule Deer worth shooting a mile from the road. It was an interesting tour. Wonderful spring at an old (treeless) homestead and this. There are some small trees about 1000 yards farther ENE.
The barely discernible hazy dark spot above the apparent horizon at the right edge is the Granite Peak area of Montana about 70 miles SE.
Surprised the slow elk have not rubbed it down. But there is little reason for them to get up there.
This shows Granite Peak a little better. The peak is SW of Red Lodge MT.
I can actually see this things shadow on Google Earth.
Dan