Sawtooth Range, Idaho Whitwater Rivers Marsh Creek Class II-III - 6 miles long (State Highway 21 to Middle Fork Salmon) Custer County Payette River - South Fork Class III-IV - 23 miles long (Grandjean to Lowman) Boise County Salmon River - Middle Fork Class III-IV - 8 miles long (Marsh Creek to Boundary Creek) Custer County