Snake River,

Snake River, the largest affluent of the Columbia River, rises among the Rocky Mountains near the western border of Wyoming, sweeps in a rough semicircle through southern Idaho, forming here the famous Shoshone Falls (q.v.), and, turning north, divides Idaho from Oregon and partly from Washington. At Lewiston it turns westward, and in southern Washington, under the name of the Lewis River or Fork, joins the Columbia, after a course of some 1050 miles. It traverses a very mountainous country, flowing through deep, lava-walled cañons, and is navigable for steamboats only to Lewiston (160 miles). In Idaho its waters are of value to the herds on the winter range. Its chief affluents are the Boise, Owyhee, Malheur, Salmon, Clearwater, and Palouse.