This dissertation focuses on the events leading to the 1968 federal prohibition of psilocybin. The goal is to show how the primary active compound in an ostensibly harmless fungus (the psilocybin mushroom) became controversial in less than a decade. The activities of Timothy Leary and Richard Alpert (later Ram Dass) were major factors in this transformation. The dissertation uses previously unpublished materials to analyze Leary and Alpert’s lives and careers through the early 1970’s. Two major components are their involvement in the “Harvard drug scandal” as well as their transformation from Harvard Professors to countercultural icons. Indeed, psilocybin first gained notoriety during the “Harvard drug scandal” when a small team of researchers, most notably Leary and Alpert, began testing the substance on a variety of human subjects including Harvard graduate students. These activities piqued the interest of Harvard undergraduates who wanted to try psilocybin for themselves. This, among other aspects of the project, drew the condemnation of other faculty and Harvard administrators. This case is theoretically interesting because unlike most illegal drugs, psilocybin was not originally linked to a threatening minority group. Rather, psilocybin’s notoriety grew out of the fact that it was being ingested by some of the nation’s most privileged young men. By the late 1960s, however, the proselytizing of Leary and Ram Dass combined with the youth and anti-war movement to demonize the drug”s users.