I remember the eruption very well. I was living in Medicine Hat, Alberta at the time , about 1000 km from the volcano. Our US cable TV stations were out of Spokane, WA so we had lots of news about the eruption, before, during and after, I will always remember the TV shots of Yakima at mid day being in almost total darkness due to the ash, It was very surreal. Even 100 km away, we had ash on our cars for several days.
In the late 90's (probably 1998 or so), I took our family and young kids on a vacation and I had to go and see the site. As others have noted, the trees along the road to the mountain were laid down like matchsticks, but even then, you were amazed at how nature was rebounding and just how much greenery was regenerating after less than 20 years.
The Visitor Center was very well done and was one of the best that I have been to. After you watched the film, the curtains were drawn and you were staring into the side of the mountain that had been blown away. A memory that I won't forget.
Do any of the PNW'ers remember Harry Truman? He was an old man (probably in his 80's), who lived near the mountain, I think at Spirit Lake? He refused to leave when the evacuation orders were issued,and was never found, so he is probably still there, buried underneath meters of debris and hot ash.
It's amazing what you remember in detail from your past!