There is a really great clip on You Tube of Clapton talking about The Band and what he thought when he heard Music From Big Pink. That hearing resulted in Eric's disbanding (ha) Cream. It's funny, because when I finally got The Band (took about a year---I wasn't quite ready for them at the time of MFBP's release), I also lost interest in Cream and their ilk (long solos, lack of ensemble playing, mediocre songs, not much harmony singing). He went to Big Pink for a couple of weeks, waiting for them to ask him to join (?!), until finally realizing they didn't need him. No duh. "Badge" is the only Cream song I ever feel myself longing to hear.
Loomis, my questioning of Cream being considered Progressive was not in response to your post directly above mine (it hadn't "appeared" yet), but rather to Ghosthouse's above it.
I also don't consider Procol Harum Progressive, even with Matthew Fisher's Classical training. One great thing about a Group/Band being so good is that they create their own genre, of which they are the only member. They were, by the way, also really good live. The first three albums are great, but when Matthew left, guitarist Robin Trower kind of took over, turning them too bluesy for my liking. Having no blues influence was one of the things that had set PH apart from the other Brits of the late 60's/early 70's.
The MC5 never really took off on the West Coast for some reason (actually, they never took off anywhere!), but their influence was pretty big in the Punk Bands that followed them a few years later (The Ramones especially). I didn't take them seriously, thinking they were just the house band for the White Panther Party! Another Group that didn't translate to the counter-culture West was Iggy & The Stooges. I don't remember either of them playing in San Francisco or Los Angeles.
The Groovies really felt like fish out of water living in San Francisco (they had nothing in common with The Grateful Dead and the rest of the hippie bands, doing short, Pop songs with no improvisation. And, they wore suits!). They went East to play a lot, ending up in England with the great Dave Edmunds producing their classic Shake Some Action album, as Loomis said, an absolute masterpiece. It has a very odd sound, very thick and dark, sort of like what Daniel Lanois gave Dylan on the Time Out of Mind album. it didn't work (for me) with Dylan, but does on Shake Some Action.