It climbs Bonaparte Creek and crosses Wauconda Pass, near Mount Bonaparte and the ghost town of Wauconda, before beginning its descent into Republic. SR 20 enters Republic on 6th Street and turns south onto Clark Avenue, the town's main street, before coming to a junction with SR 21. The highway turns northeast onto the Sherman Pass Scenic Byway, carrying the concurrent SR 20 and SR 21, and follows the Sanpoil River. SR 21 leaves the byway at Sanpoil Lake, while SR 20 travels into the Kettle River Range along O'Brien Creek. The highway dips south into the Colville National Forest and climbs the ridge, crossing Sherman Pass in a series of hairpin turns. The pass, located above sea level, is the highest in the state. SR 20 descends along Sherman Creek towards Franklin D. Roosevelt Lake on the Columbia River, which it crosses on a highway concurrent with US 395. The two routes travel east through Kettle Falls, intersecting SR 25, and follow the Colville River upstream to the city of Colville.