Chief Mountain, or Nínaiistáko, rises at the edge of Glacier National Park and the Blackfeet Indian Reservation in northern Montana, where its isolated profile makes it a major landmark along the Rocky Mountain Front. Geologically, it is a klippe left from the Lewis Overthrust, with ancient Precambrian rock resting atop much younger Cretaceous shale. Sacred for centuries to the Blackfeet and other Native peoples, it remains a ceremonial and religious place. Known to explorers by the late 18th century and partly included in Glacier National Park in 1910, it also became noted for difficult climbing, including an 1892 ascent that found ceremonial remains on the summit.