Mount Saint Helens
So yes, our first page in the Oregon trip is in fact in Washington. Mount Saint Helens is however an easy day trip from Portland and in fact you can see it from Portland if the weather co-operates. We entered the monument from the west side. The road from I-5 follows the Toutle River up to the volcano. It's a little confusing here. Due to budget cuts the NPS has actually given up much of the area. Those former visitor centers have been claimed by other groups and now you pass the Washington State visitor center as well as a county visitor center and another one run by the logging industry. Of these we have to recommend the one run by the logging industry as it has the nicest playground and great views. That would be the third visitor center you pass.
There is also an NPS visitor center which sits adjacent to the volcano research area and it is literally just downhill from the summit (or what remains of it). This is actually where you want to be (eventually). If you watch the film here it will give you a decent intro to the events of 1980 and then at the end the screen will dramatically rise to reveal the summit of the volcano. It'll look just like this on a cloudy day. Also, you've already seen the dramatic view because you arrived here somehow. Anyway, it's worth a visit to the NPS building, there are plenty of harrowing stories from the day of the eruption on display in there.
Just across from the visitor center is the spectacular (in June at least) wildflower trail. This is little more than a scenic route back to the parking lot but it truly is scenic.
There would probably be many great views of the mountain if there were any views of the mountain. We had some tantalizing glimpses throughout the day for a couple seconds at a time but the clouds were generally always present. On the other hand, the summit is largely ruined since the eruption and you can't get any closer than the visitor center now. Elsewhere in the monument are assorted hiking trails and picnic areas.
Here is the Toutle River closer to the summit. This was one of the log-choked massively flooded rivers shortly after the eruption (for those old enough to remember it). As you can see the valley is quite a bit larger than the current size of the river.
We stopped at the hummocks trail which is a little west of the summit. We thought this was the nicest area in the park actually. It helped that it was late June and everything in sight was blooming. The hummocks that the trail is named after are these mounds of volcanic residue. Most of them have a series of small ponds at the base now as well.
The trail is only about 3 miles (5 km) long but covers a remarkable variety of terrain. The hummocks are still mostly open land with volcanic rocks and some mosses. In between are forested segments and some grassland.
There is also an extensive beaver pond area where many people (not us) reported seeing several beavers. Somewhere around here the weather decided to start raining on us persistently for the remainder of the hike.
There's also a nice section of heavy ferns that is remniscient of Olympic further north.
It should be mentioned that there is an east entrance to the park as well. There are no road connections between the two sides. We spent some time trying to plan a route that would allow us to visit both sides in the same day and ultimately dismissed it as impractical and a ridiculous amount of driving.