At , Diamond Peak is the highest peak in the wilderness. The next highest named peaks are Mount Yoran at and Lakeview Mountain at . Diamond Peak is a shield volcano formed as the entire Cascade Range was undergoing volcanic activity and uplift. Glaciers carved the large volcanic peak, and when they receded, the bulk of the mountain remained, with snowfields near the summit and dozens of small lakes surrounding the peak. These lakes range from one to in size. Approximately of the Pacific Crest National Scenic Trail pass through this wilderness. Another of trail, including the Diamond Peak Trail, stretches the length of the west side of the peak.