There was a large Indian camp on the Platte River near the present site of Casper, Wyoming, that was known to the early trappers as the Old Sioux Camp. To the north, near the present site of Bridger, Montana, on Clark's Fork River, was another large and well known Indian camp. They were crossroads of the nation and trails led in all directions. Halfway between was Tensleep. The Indians measured distance by the number of "sleeps" it took to get from one place to the other. It was "ten sleeps" from there to each of the main camps.

The Indian writings for "Ten Sleeps" were found on the wall of a cave just 3 miles east of Tensleep.