Marijuana is the most controversial drug of the twentieth century. Smoked by generations of musicians, students, and workers to little discernible ill effect, it continues to be reviled by the vast majority of governments around the world. Director Ron Mann recounts how marijuana has become the focus of jubilant celebrations and legal repression through the decades. Mixing hysterical anti-marijuana archival footage with playful psychedelic graphics by underground cartoonist Paul Mavrides, Mann utilizes the vocal talents of grass activist Woody Harrelson to narrate the darkly comic tale of how grass became the drug of choice not only for pot heads but also for U.S. federal officers. Grass features a motley crew of characters ranging from the first head of the U.S. Federal Bureau of Narcotics and arch-conservative Presidents Richard Nixon and Ronald Reagan on the right to politicians Fiorella La Guardia and Jimmy Carter and grass victims Robert Mitchum and Gene Krupa on the left.