The Klamath River is a 257-mile long river in southern Oregon and northern California. Beginning near Klamath Falls in the Oregon high desert, it flows west through the Cascade Range and Klamath Mountains before reaching the temperate rainforest of California's North Coast, where it empties into the Pacific Ocean. The Klamath River is the third-large…The Klamath River is a 257-mile long river in southern Oregon and northern California. Beginning near Klamath Falls in the Oregon high desert, it flows west through the Cascade Range and Klamath Mountains before reaching the temperate rainforest of California's North Coast, where it empties into the Pacific Ocean. The Klamath River is the third-largest salmon and steelhead producing river on the west coast of the contiguous United States. The river's watershed – the Klamath Basin – encompasses more than 15,000 square miles, and is known for its biodiverse forests, large areas of designated wilderness, and freshwater marshes that provide key migratory bird habitat.