Wonder if that's the Cheyenne reservation on Wind river?
There are two federally recognized Indian tribes in Wyoming today.
Wyoming's Shoshone and Arapaho tribes share a single Indian reservation....the Wind River rez!
Interesting bit of NA history of the area.
Nearby Crowheart Butte was the site of a battle between the Crow and Shoshone American Indian tribes in 1866. According to legend, following a five day battle for rights to the hunting grounds in the Wind River Range, Chief Washakie of the Shoshone and Chief Big Robber of the Crow agreed to a duel, with the winner gaining the rights to the Wind River hunting grounds. Chief Washakie eventually prevailed, but he was so impressed with the courage of his opponent, that rather than scalp him, he instead cut out his heart and placed it on the end of his lance.