Mount St. Helens Spirit Lake Memorial Highway — Castle Rock to Johnston Ridge

The highway leaves I-5 at Castle Rock and follows the North Toutle through hummocks — the 100-foot clay mounds the landslide left behind. The Hummocks and Science Learning center overlooks mark the first views of the volcano. Beyond Coldwater the road climbs hard through the gray zone, switchbacking up the ridge with Spirit Lake glimpsed through the trees, and tops at the observatory — where ranger talks run hourly in season and the crater sits a half mile away. Everything above 1,500 feet on the north side is a protected volcanic monument: no fuel, no water, wind exposure on the ridge — ride it in morning light before the tour buses. The road is open to Johnston Ridge most of the year but closes at theHummocks in winter.