Researchers have long been concerned with cancer in what has been called the tropics, developing world, and low-and middle-income countries. Global health advocates' recent calls to attend to an emergent cancer epidemic in these regions were only the latest effort in this long history. Researchers, known as geographical pathologists, sought to determine the etiologies of cancer and other non-infectious diseases between the 1920s and the 1960s by comparing their occurrence across different environments. The geographical pathologists used the concept of the environment to analyze the influences that natural and artificial surroundings had on health. While the international network of geographical pathology fostered medical thinking about environmental health in the early and mid-twentieth century, the very meaning of environment, alongside the scientific methods for studying the environment, changed in this period. In the 1960s, epidemiology, previously used for the study of infectious diseases, displaced geographical pathology as the cohesive framework of cancer research. This signaled a shift in research focus, from one dedicated to diagnostics and the environment to one centered on population and statistical studies. This article shows that it was not the lack of knowledge about cancer in the developing world but rather specific configurations of knowledge that shaped which cancer interventions in the developing world researchers and public health officials conceived. I confirm that the manuscript is comprised of original material that is not under review elsewhere, and that the studies on which the research is based has been subject to review by the Committee on the Use of Humans as Experimental Subjects (COUHES) of the Massachusetts Institute of Technology.