My dissertation is a social, political, and cultural history of leprosy in the United States around the turn of the twentieth century. I examine the United States’ evolving immigration policy and imperial objectives through the lens of American approaches to leprosy control, which I define as the attempts of public health officials, federal politicians, physicians, missionaries, and other historical actors to construct narratives about leprosy and manage the movement of people with the disease. Especially considering the lack of medical consensus regarding proper treatment and containment, I argue that debates over controlling leprosy made the disease an exaggerated proxy for the myriad public health dangers connected to Asian immigration and imperial expansion, especially in the Pacific. Though rare across most of the mainland, racialization of the disease and its classification as “tropical” shaped the imagined threat it posed to white Americans and the public health policies it shaped.