One could argue Iron Butterfly helped launch metal by bridging from psychedelic rock to their then new heavyness. I think most people might recognize In-A-Gadda-Da-Vida and assume they're a hippie, one-hit wonder.

The Guess Who and Frank Zappa were damn important too.

Btw, one of the most important locations for counterculture rock influence was the Hollywood Landmark Motor Hotel (today: The Highland Gardens Hotel). Jim Morrison, Jimi Hendrix, Pink Floyd, Janis Joplin (who lived and died there), and Alice Cooper were all there... oh and Shep Gordon.