"Marijuana was legal for much of U.S. history and was recognized as a medicine in 1850. Opposition to it began to gather and, by 1936, 48 states had passed laws regulating pot, fearing it could lead to addiction. Anti-marijuana literature and films, like the infamous "Reefer Madness," helped fan those fears. Eventually, pot was classified among the most harmful of drugs, meaning it had no usefulness and a high potential for addiction." Excerpt from 4 Americans get pot from US government, an article Ima see on Yahoo today.