East of McCall and Cascade, Idaho.
If you are going from Boise, take Highway 55 north. Just out of Cascade, turn east (right) on the Warm Lake Highway. It will take you to the upper end of the South Fork Salmon River. There is a road that parallels the South Fork Salmon River and runs downstream.
To access the lower end of the South Fork Salmon River, take the road that runs east out of McCall towards Yellow Pine.