Snow 1854


Dr. John Snow first recognized the potential of applied cartography while mapping a London cholera outbreak in 1854. Dr. Snow is credited with demonstrating the water-borne origin of cholera through his mapping of the epidemic in London during the 1850's. In 1849, Snow published an essay, ‘On the Mode of Communication of Cholera,’ in which he stressed the importance of sewage-free water as a preventative measure against cholera. The second edition of this essay included a map of the distribution of deaths from cholera in the Broad Street district of London in 1854, with the Broad Street pump at the center of the map. Snow insisted that the handle of the pump be removed on September 8. No new cases occurred after this date, proving that cholera was being spread directly through the water from the Broad Street pump. Not only did the map help prove his theory, but it also inspired action which had concrete medical results, marking a shift in the field of medical cartography as maps became more integrated into public health and the practice of medicine.

Despite the fact that geography is a major indicator of health status and driver of health disparities, geographic tools are extremely underutilized in the field of public health. Inspired by the lessons from Broad Street, we believe in leveraging the power of maps to visualize information, identify patterns, and make decisions.