What factors in the 1960's and 1970's led to what has been called the sexual revolution?

The sexual revolution of the 1960s and 70s largely affected the way American society is now. In the 1960s something called "free love" came about, deeming young people as hippies. The Hippies preached that the beauty of sex and love was a form of art. Thus this lead the way for more pre-marital sex, and a higher rate of teen pregnancies. New drugs such as LSD, were created and experimented with, causing the now war on drugs.