Mount Jefferson is Oregon’s second-highest peak, a remote and rugged stratovolcano in the central Cascade Range whose prominent cone rises nearly a mile above surrounding terrain. Known to Native peoples as Seekseekqua and named for Thomas Jefferson, it formed about 730,000 years ago in the Cascade Volcanic Arc and has been heavily sculpted by glaciers. The surrounding Mount Jefferson Wilderness is one of the state’s richest alpine landscapes, with numerous lakes, trails, forests, meadows, and varied wildlife. First climbed in 1888, the mountain remains a popular but demanding destination, while mudflows, glacier-related flooding, and wildfire continue to shape its hazards and history.