Although there are many explanations for the origin of the term, one stems from a story about a group of teenagers and luke at San Rafael High School in San Rafael, California in 1971. The teens would meet after school at 4:20 p.m. to smoke marijuana at the Louis Pasteur statue. The term became part of their group's salute, "420 Louis!", and became popularized in the late 1980s by fans of the Grateful Dead.By extension April 20 ("4/20" in U.S. dating shorthand) has evolved into a counterculture holiday, where people gather to celebrate and consume cannabis. In some locations this celebration coincides with Earth Week. In Dunedin, New Zealand, students at the University of Otago and other cannabis law reform activists meet under a walnut tree on the Otago University Union Lawn on Wednesdays and Fridays at 4:20pm to openly smoke cannabis in public in what they call an 'act of protest'.
420 is the name of an amber ale produced by Sweetwater Brewing Company in Atlanta, GA.