Johnstone Peak is between the town of Ketchum and Hyndman Peak. It is 9949 feet high. Typically it is the mountain you will see in front of Hyndman when pictures are taken from Sun Valley. Not sure what real reason there is to do it other than. 'It's there'. The back side from Pioneer Cabin is cooler looking than the front side which is why I decided to do it. Terrific weather for mid October and a pretty decent hike.