Old Man of the Hills is an 8,229-foot mountain on Montana’s Rocky Mountain Front, where the plains meet the sharply rising Rockies. In the Lewis and Clark National Forest near the Bob Marshall Wilderness, it stands out for its steep local relief, with the summit rising about 2,800 feet above Dupuyer Creek in only one mile. Water from its slopes feeds Dupuyer Creek and eventually the Marias River. Geologically, it belongs to the southern Lewis Overthrust, where sedimentary rocks formed from the Precambrian to the Jurassic were later pushed eastward over younger rock during the Laramide orogeny. The mountain is also marked by an alpine subarctic climate with severe winters.