Virtually every American alive has at some point consumed at least one, and very likely more, consciousness altering drug. Even those who actively eschew alcohol, tobacco, and coffee cannot easily avoid the full range of psychoactive substances pervading the culture. If the use of drugs is a constant in American history, the way they have been perceived has varied extensively. Just as the corrupting cigarettes of the early-20th century became the glamorous accessory of Hollywood stars and American GIs in the 1940s, only to fall into public disfavour later as an unhealthy and irresponsible habit, the social significance of every drug changes over time. This work shows how the identity of any psychoactive substance owes as much to its users, their patterns of use, and the cultural context in which the drug is taken, as it owes to the drug's documented physiological effects. Rather than seeing licit drugs and illicit drugs, recreational drugs and medicinal drugs, ""hard"" drugs and ""soft"" drugs as mutually exclusive categories, it challenges readers to consider the ways in which drugs have shifted historically from one category to another.