The Siskiyou Mountains are a coastal subrange of the Klamath Mountains, and located in northwestern California and southwestern Oregon in the United States. They extend in an arc for approximately 100 miles from east of Crescent City, California, northeast along the north side of the Klamath River into Josephine and Jackson counties in Oregon. The mountain range forms a barrier between the watersheds of the Klamath River to the south and the Rogue River to the north.