Historically used as a renewable resource and a treatment for both minor and terminal illnesses, cannabis (variously called marihuana, marijuana, or hemp) was the harbinger of a contradictory attitude in the United States toward controlled substances. This pervasive weed can be smoked or eaten as a mild intoxicant, and has become the third most popular recreational drug after alcohol and tobacco. Marijuana was once an integral part of early American agrarian society, but advances in synthetic manufacturing eliminated its industrial applications and threatened its highly-debated medicinal use as well. Modern physicians are intrigued by marijuana's efficacy, but a wave of drug hysteria that started in the 1930s effectively negated the drug's positive reputation. Despite their checkered history, hemp and marijuana remain important aspects of American popular culture.

Cannabis generally grows in two forms: hemp and marijuana, the former producing more oil and fiber, the latter producing more of...