Bighorn Mountain Sink, Gravelly Range, MT: Closing the Case on an Old Lead February 11, 2021October 11, 2020 This content is for NRMG members only.Log In Register Related posts: Searching for Caves in the Northern Rocky Mountains Possibly The Highest Cave In Montana Montana’s Highest Cave Which Cave Mountain Cave Are We Talking About? Peterson Meadow: Better Late Than Never, Part 1 Pryor Mountain Karst Inventory