Castle Rock Spire is one of the tallest peaks in Montana’s Beartooth Mountains, rising within the Absaroka-Beartooth Wilderness in Custer and Gallatin National Forests. At 12,545 feet, it ranks as the seventh highest summit in the state and among the tallest in the Beartooth range. The mountain stands just west-southwest of Castle Mountain, and the Sundance Glacier covers its north slopes, reinforcing its rugged high-alpine setting.