This article is about the Snake River in the northwestern United States. For other uses, see Snake River (disambiguation)

The Snake River is a river in the western part of the United States. The Snake River is 1,038 miles (1,670 km) in length, and is the Columbia River's main tributary. The Lewis and Clark expedition (1803-6) was the first major U.S. exploration of the river, and the Snake was once known as the Lewis River.

The Snake originates near the Continental Divide in Yellowstone National Park in NW Wyoming and flows south to Jackson Lake in Grand Teton National Park and past the town of Jackson. The river flows down Snake River Canyon , then enters Idaho at the Palisades Reservoir and joins with the Henrys Fork River near Rigby. Note: residents of eastern Idaho generally call the Snake prior to this joining the "South Fork of the Snake", distinguishing it from the Henrys Fork.

The Snake then swings down in an arc across southern Idaho, forming the Snake River Plain. In doing so it passes through the city of Idaho Falls and the American Falls Reservoir and then past Twin Falls and Boise to the Idaho/Oregon border. It then flows north through Hells Canyon, and past the cities of Lewiston, Idaho and Clarkston, Washington. It then turns into Washington, passes through many hydroelectric dams and finally joins the Columbia River near Pasco, Washington.

Tributaries of the Snake include the Henrys Fork River, the Boise River, the Salmon River, and the Clearwater River.

The Snake River's many hydroelectric power plants are a major source of electricity in the region. Its watershed provides irrigation for various projects, including the Minidoka, Boise, Palisades, and Owyhee projects by the U.S. Bureau of Reclamation, as well as a variety of private projects such as at Twin Falls.

The Snake runs through a number of gorges, including one of the deepest in the world, Hells Canyon, with a maximum depth of 7,900 feet (2,410 m).

The name "Snake" possibly derived from an S-shaped (snake) sign which the Shoshone Indians made with their hands to mimic swimming salmon. Variant names of the river have included:

• Great Snake River
• Lewis Fork
• Lewis River
• Mad River
• Saptin River
• Shoshone River
• Yam-pah-pa

Counties through which the Snake flows are:

• Franklin County, Washington
• Walla Walla County, Washington
• Columbia County, Washington
• Whitman County, Washington
• Garfield County, Washington
• Asotin County, Washington
• Nez Perce County, Idaho
• Wallowa County, Oregon
• Idaho County, Idaho
• Adams County, Idaho
• Baker County, Oregon
• Washington County, Idaho
• Malheur County, Oregon
• Payette County, Idaho
• Canyon County, Idaho
• Owyhee County, Idaho
• Ada County, Idaho
• Elmore County, Idaho
• Gooding County, Idaho
• Twin Falls County, Idaho
• Jerome County, Idaho
• Cassia County, Idaho
• Minidoka County, Idaho
• Blaine County, Idaho
• Power County, Idaho
• Bingham County, Idaho
• Bannock County, Idaho
• Bonneville County, Idaho
• Jefferson County, Idaho
• Lincoln County, Wyoming
• Teton County, Wyoming

Source for some material: U.S. Geological Survey