Woody Harrelson narrates this documentary about the history of marijuana in 20th century America. Beginning with clips from educational films and exploitation pictures that show how marijuana can lead to crime, insanity, and harder drugs, Grass also documents the exploits of Harry Anslinger, who became America's first drug czar and waged a lifelong war against marijuana use in the United States. As the repressive environment of the 1930s and 1940s gave way to the beat era of the 1950s and the hippie uprisings of the 1960s, attitudes towards marijuana became more lenient, and several states relaxed their laws regarding the drug; but the election of Ronald Reagan, and his wife Nancy's famous "Just Say No" campaign, put many pro-pot activists back in the starting blocks. Director Ron Mann takes a decidedly pro-marijuana position in this film, though he does so with more humor than militance (the end credits note "No hippies were harmed in the making of this film").