Siskiyou County is located in inland northern California, adjacent to the Oregon border. As the fifth largest county in California by area, Siskiyou County features spectacular natural beauty and scenic cities and towns including Yreka--the County Seat, Mt. Shasta, Weed, Dunsmuir, McCloud and Tulelake as well as Butte Valley, Scott Valley, Shasta Valley and the Klamath River Corridor. Greater than 60% of the land within the County is currently managed by agencies of the Federal and State governments. These include: The U.S. Forest Service; Bureau of Land Management; U.S. Fish and Wildlife Service; and California Department of Fish and Game. These lands are maintained in various National Forests; Parks; Wilderness Areas; National Grasslands; National Wildlife Refuges; and State Wildlife Areas. Next to the Appalachian region, Siskiyou County is one of the most ecologically diverse regions in the world. It sites the "meeting" of several western mountain ranges and the transitional mixing of various habitat types. Geographically, it has considerable vertical variance in elevation, hydrological and soil conditions. Portions of the County are heavily influenced by volcanic forces. Siskiyou County also has several areas that were unaffected by ancient glacial flooding. Siskiyou County is the fifth largest county by area and the population as of 2010 was 44,962 which is roughly a 11,000 population increase since 1970. The origin of the name Siskiyou is not known. In one version it is Chinook jargon for "bob-tailed horse." In another it comes from the French name Six Callioux meaning "six stones" and that Stephen Meek, an early Hudson Bay Company trapper used the name for a Klamath River crossing near Hornbrook.