The use of cocaine began in the United States during the mid-1880s, reached a peak between 1900 and 1915, and then went into a sustained period of decline. By the end of the 1920s, most observers regarded cocaine as a purely historical phenomenon. Cocaine remained at the margins of the American drug scene for over four decades, yet historical accounts have not attempted to explain why the once-popular drug disappeared. The overlap between the declining-use trend and the shift from a legal, regulated market to an illicit market has supported the assumption that the start of legal prohibition successfully ended cocaine use. This study examines several theories of cocaine's decline, and concludes that legal prohibition was only partly responsible. Stricter laws regarding distribution eliminated the legal market, and made the cocaine that remained through illicit channels more expensive and harder to find. Nevertheless, this study suggests some qualifications to the conclusion that prohibition was a success. First, legal prohibition did not change the nature of the cocaine business as dramatically as is often assumed. Rather, prohibition merely accelerated trends that had begun much earlier as a result of regulation and informal controls. Second, the "success" of legal prohibition was dependent upon a number of unique historical circumstances, including the interest and ability of cocaine manufacturers to exploit new legal markets outside the United States, and the ready supply of cheap heroin for domestic drug markets. The conclusion of the first cocaine era was neither an inevitable end to a "cycle" of drug use, nor the outcome of a well-planned set of drug policies, but the product of a combination of national and international trends.