The literature and Harrison Zwiebel as the Narcotics 1995; beginning Benson Tax of and Act the Rasmussen of US 1914 government's is 1997; widely Libby viewed war 2006; on in drugs the Francis scholarly (Miron and literature as the beginning of the US government's war on drugs (Miron and Zwiebel 1995; Benson and Rasmussen 1997; Libby 2006; Francis and Mauser 2011; McNamara 2011). An essay by Peter Boettke, Christopher Coyne, and Abigail Hall (2013) is an exception that dates the war's start to the Pure Food and Drug Act of 1906. However, the problems that the Harrison Act was intended to address can be directly traced to the unintended consequences of antidrug policies adopted by state governments and the federal government in the nineteenth century. This paper documents these nineteenth-century antidrug policies and uses an economic theory of the dynamics of intervention to explain how these policies led to the adoption of the Harrison Act. These nineteenth-and early-twentieth-century policies represent the beginning of the US government's war on drugs.