Cascade–Siskiyou National Monument protects 114,000 acres where the Cascade Range meets the Siskiyou Mountains in southwestern Oregon and northwestern California, a landscape noted for exceptional biodiversity. Created in 2000 and expanded in 2017, it became the first national monument in the United States established solely to preserve biodiversity, and later court rulings upheld that larger designation. Native peoples lived here for thousands of years, and archaeological evidence links nearly 100 sites to the Modoc, Klamath, and Shasta tribes. The area also contains remnants of 1880s mining, landmarks such as Pilot Rock and the Soda Mountain Wilderness, and continuing debates over habitat protection, recreation, grazing, timber, and private inholdings.