Mt. Pennell is the second highest peak in the Henry Mountains. Several deep canyons cut the sides of the mountain, which on the higher slopes supports oak, Ponderosa pine, subalpine fir, spruce, Douglas fir, and aspen. Four distinct biological life zones are within the WSA due to nearly 5,000 feet of change in elevation. Portions of the WSA are summer range for the Henry Mountain bison herd, and bison are frequently seen in the vicinity of The Horn.