Diamond Peak is an 8,748-foot volcano on the Cascade Crest in central Oregon, dominating the Diamond Peak Wilderness between the Deschutes and Willamette national forests. Formed late in the Pleistocene from overlapping cones of mainly basaltic andesite, it produced lava flows and cindery material and shows no evidence of eruption within the last 10,000 years. Glaciation heavily shaped its present form, carving cirques and leaving moraines and talus. Named in July 1852 for pioneer John Diamond after a scouting climb tied to the future Free Emigrant Road, the peak is linked to migration into the upper Willamette Valley. Today it is valued chiefly for wilderness travel and hiking.