Chief Mountain is located in the U.S. state of Montana on the eastern border of Glacier National Park and the Blackfeet Indian Reservation. The mountain is one of the most prominent peaks and rock formations along the Rocky Mountain Front, a 200 miles long overthrust fault, known as the Lewis Overthrust, which extends from central Montana into southern …Chief Mountain is located in the U.S. state of Montana on the eastern border of Glacier National Park and the Blackfeet Indian Reservation. The mountain is one of the most prominent peaks and rock formations along the Rocky Mountain Front, a 200 miles long overthrust fault, known as the Lewis Overthrust, which extends from central Montana into southern Alberta, Canada.