lake, north-central Washington, U.S., extending 55 miles (88 km) through a glacier-carved valley on the eastern edge of the Cascade Range. Lying just outside North Cascades National Park near the confluence of the Methow and Columbia rivers, Lake Chelan is—at a depth of 1,486 feet (453 metres)—the third-deepest lake in the United States. The southeastern end of the lake, where the small towns of Chelan and Manson are located, is heavily visited; the northwestern section lies in a wilderness area in an isolated mountain valley and is inaccessible by road. A portion of the lake was designated in 1968 as a National Recreation Area.