Region
Montana
Powder River County
12
Powder River County (Mont.)
8
Wyoming
8
Big Horn County
6
Rosebud County
6
Campbell County
5
Campbell County (Wyo.)
5
Sheridan County
2
Sheridan County (Wyo.)
2
Big Horn County (Mont.)
1
Birney Quadrangle
1
Birney quadrangle
1
Broadus quadrangle
1
Bull Mountain Region
1
Fort Union Formation
1
Miles City Region
1
Miles City Region (Mont.)
1
North Dakota
1
Powder River Basin (Wyo. and Mont.)
1
South Dakota
1
Treasure County
1