Woodstock was a massive music festival know for many things, especially drugs. Woodstock is especially infamous for the mass consumption of lsd and cannabis. However even though so many people were doing it, it was causing some large problems at the festival and even now.
Lysergic acid diethylamide, also know as acid, is a potent hallucinogenic drug synthisized from lysergic acid. Lysergic acid can be found growing on rye and other grains. LSD is such a potent drug it is normally micro dosed.