The Selway River is a large tributary of the Middle Fork of the Clearwater River in the U.S. state of Idaho. It flows within the Selway-Bitterroot Wilderness, the Bitterroot National Forest, and the Nez Perce National Forest of North Central Idaho. The entire length of the Selway was included by the United States Congress in 1968 as part of the Nation…The Selway River is a large tributary of the Middle Fork of the Clearwater River in the U.S. state of Idaho. It flows within the Selway-Bitterroot Wilderness, the Bitterroot National Forest, and the Nez Perce National Forest of North Central Idaho. The entire length of the Selway was included by the United States Congress in 1968 as part of the National Wild and Scenic Rivers Act.