A woman named Psylvia dances in the middle of a crowd. (Bill Eppridge/Time & Life Pictures/Getty Images)

The half a million people who were at Woodstock will tell you that those three days of peace and music in the mud and rain, when they listened to the songs of that generation’s music “greats,” often naked, often stoned, changed rock and roll forever. Many believe it altered the mood of a generation, too.

Coming into 1969, Martin Luther King, Jr., Malcolm X, President John F. Kennedy and Sen. Robert F. Kennedy had all been assassinated. Chicago and other American cities had been the scenes of riots. Some political activist groups were turning violent. America was still in the midst of the Vietnam war.

It was “a very dark time in America,” Michael Lang, co-ordinator of the Woodstock Music and Arts Festival, which took place 42 years ago today, once said.

“And then along came Woodstock and it was this magical moment of peace and harmony and I think it gave everyone the inspiration that perhaps things could be just a little bit better.”

Below are photos from LIFE.com, whose photographers were at the festival on those three fateful days from Aug. 15-18, 1969:

The beat of a new generation. (LIFE.com/Bill Eppridge/Time & Life Pictures/Getty Images)