Siskiyou County is a county located in the northernmost part of the U.S. state of California. As of the 2020 census, the population was 44,076. Its county seat is Yreka and its highest point is Mount Shasta. It falls within the Cascadia bioregion. Siskiyou County is in the Shasta Cascade region along the Oregon border. Because of its outdoor recreation, Mt. Shasta, McCloud River, and Gold Rush era history, it is an important tourist destination within the state.