In which astrological era did the concept of "open" sexuality begin?

I know it had to be sometime after the 50s, but I know that in the 70s sexuality (in the US at least) wasn't discussed and acted upon quite openly among the older persons. The younger persons were burning bras, though. I wondered when this concept really started to flourish, and if it was a reflection of Saturn, Uranus, Neptune, or Pluto, or a combination of those. (please be specific)