I don't think this sign was up 1000 years ago for the bison. This is looking to the WSW. That is Square Butte on the right which is where I thot this Buffalo Jump was located.

Square Butte is a laccolith formation, a type of igneous intrusion where magma pushed up overlying rock layers.
It is a High Potential Historic Site along the Lewis and Clark National Historic Trail, first noted by Lewis in 1805.