Hard Rock established itself in the 1970's when bands like Led Zeppelin for example got away from the more acid rock bands like
Jimi Hendrix, Cream, Iron Butterfly who were more psychedelic and less blues. It was Led Zeppelin who
set the prototypical hard rock sound that would be imitated from the 1970's to the present. Hard Rock is also much more commerical friendly than Heavy
Metal.
Led Zeppelin, Aerosmith, Queen,
AC/DC, Thin Lizzy, Blue Oyster Cult, Alice Cooper, Pink Floyd,
Heart, Deep Purple, Mountain, Pearl
Jam, Stone Temple Pilots.