Siskiyou

Siskiyou is a regional designation in the Pacific Northwest, referring to the area surrounding the Siskiyou Mountains that straddle the northern California–Oregon border. The term is used to describe a geographic, ecological, and cultural zone that is part of the larger Klamath-Siskiyou bioregion. The name is common in references to the mountains, counties, and protected areas in this part of the two states.

The Siskiyou Mountains run along the boundary between California and Oregon and form a rugged, ecologically diverse landscape. The region includes lowland woodlands, river valleys, and high-elevation habitats, with varied geology that includes serpentine soils and a mix of metasedimentary and volcanic rocks. Climate ranges from wet coastal influence to drier inland conditions, with snow in the higher elevations.

Biodiversity in the Siskiyous is notable for high plant diversity and numerous endemics, protected in national forests and state parks. The area hosts old-growth conifer forests and habitats for species such as salmon and other anadromous fish in the Klamath River system and its tributaries. Serpentine soils contribute to unique plant communities.

Indigenous peoples in the region include the Karuk, Yurok, Shasta, and Klamath nations, among others, with long histories of harvesting, trade, and stewardship. European-American settlement accelerated in the 19th century, driven by mining, logging, and later agriculture, shaping land use and demographics.

Siskiyou County, California, contains the city of Yreka, its county seat. The Cascade-Siskiyou National Monument protects ecologically transitional areas at the convergence of the Cascade Range and the Siskiyou Mountains, reflecting the region’s status as a biodiversity hotspot.

The origin of the name Siskiyou is uncertain, but it has been in use since the 19th century to label the mountains, counties, and other regional features in northern California and southern Oregon.