I am posting this tonight even though the actual anniversary is not until tomorrow.
The Woodstock Music Festival began on Max Yasgur's farm outside of Bethel, NY. Eventually there were between 400 to 500 thousand people living in the mud, grooving to some of the best music, smoking a LOT of dope.
http://www.youtube.com/watch?v=a8eiL25BjkY
My $0.02
Mike