The Snake River is the chief branch of the Columbia River. The Snake River rises in Wyoming near the Continental Divide in Yellowstone National Park. The river then flows south through Grand Teton National Park. It bends west and flows across the Snake River Plains of southern Idaho.
The Snake River turns north at the Oregon border. The river forms part of the boundary between Idaho and Oregon and flows through Hells Canyon. At Lewiston, Idaho, the Snake turns west and flows through southeastern Washington. The Snake River joins the Columbia River near Pasco, Washington, 1,038 miles (1,670 kilometers) from its source.