The fee is $8 per adult, but federal interagency recreation passes get you free entry (e.g. America the Beautiful Pass). Unlike at other trailheads, do not leave the pass in your car. Take it with you into the Johnston Ridge Observatory and claim your free entry (a wristband).
We arrived at the Johnston Ridge Observatory around 11am on a Saturday. The parking lot was about half full, but it is massive, so finding a space was not an issue.
There were Ranger talks scheduled every hour from 11:10am until 4:10pm (all starting at 10 minutes past the hour), so we went to a talk first, which was very interesting.
We began the Eruption Trail around midday. The first half of the trail was very busy, but most people seem to turn around at the summit rather than complete the loop, so the second half is much quieter, and still has some great views.
The views of Mt. St. Helens are spectacular! Unfortunately the cloud never completely lifted, so we could not see inside the crater, but we got clear views of the summit and the vast valley in-between.
With the help of binoculars, we were able to see some wildlife: a Roosevelt Elk, ~1 mile away having a sit down in the plains; and a herd of Mountain Goats, ~3 miles away on the upper right slope of Mt. St. Helens!
We spoke with a volunteer, who was very knowledgeable about the area, and helped us with spotting some of the wildlife. He had brought a powerful scope on a tripod, which he kindly let us and others use. (Thank you!)
Don’t forget to look behind too. On the hills facing away from Mt. St. Helens, many of the flattened trees from the eruption are still visible. It is also interesting to see how some areas were shielded from the blast, and so have much more greenery.
The wildflowers were also in full bloom, with a sea of red all around.