Even though Mexico has been an important player in the international drug trade, this country's history in such illegal ventures has been insufficiently studied. In an effort to begin to understand how and when the country began to be an active participant in such illicit markets, this article first analyses regulations introduced in the United States regarding drug and alcohol consumption, marketing and production and assesses their impact on the Mexican side. Secondly, it argues that Mexico's participation in the narcotics trade, the routes that have developed and the Mexican states involved in this traffic have roots that can be traced to the beginning of the twentieth century at least.