Extinct for some two million years, a volcano with an elevation of once dominated this landscape. The eroded remnant of this volcano consists of rugged peaks that average over elevation. The highest point among them is Gilbert Peak, at with a prominence of . On the shaded northern slopes of the major peaks are the Packwood, McCall, Conrad, and Meade glaciers. The wilderness is drained by the North and South Forks of the Tieton, Cispus, and Cowlitz rivers and their tributaries. The lowest point in the wilderness is near Packwood Lake at 2,920 feet (890 m).