Spirit Lake Memorial Highway to Mount St. Helens is a 52 mile moderately trafficked out and back trail located near Castle Rock, WA that features a river and is good for all skill levels. The trail is primarily used for scenic driving and is accessible year-round.
Scenic highway to Mt. St. Helens national volcanic monument. The road to Mt. St. Helens.
I've always enjoyed taking this highway for a Sunday drive. If your hobby is geocaching this is a fantastic trip. Many visitor centers opened in the summer with many places to stop and picnic. A great drive to see the rebirth of the ecosystem post eruption.