This trip down to Seaquest State Park, just outside of Castle Rock, Washington, took place in late June of 2021. The park is located on Spirit Lake Highway (Highway 504), which ends at the Johnson Ridge Observatory looking out at Mount Saint Helens. Its about an hour , 55 mile drive one way from I-5, but is worth the drive if you have the time. Keep in mind that the last gas station is located in Toutle, about ten miles in, so stop if your car is low on gas.
This park is a great place to stay for the blast zone side of the mountain. It quiet, and well maintained. Right across the road, and is accessible via a tunnel from the campground, is a visitor center and short trail. The visitor center was closed due to a remodel when we visited, but is supposed to open fall of 2021.
If you want to get to the back side of the mountain, this is probably not your best bet for a place to stay. It is another hour south to Woodland, Washington to get to Highway 503 and the back side of the mountain. From Woodland, it is still quite a distance to most of the “attractions” that you may want to see. For that type of trip I would consider staying farther south or in a National Park campground (of which there are plenty around).
