One of the first uses of a map to display epidemiological data was this dot chart (from Tufte, 1983, p. 24) by Dr. John Snow (1855) showing deaths from cholera (dots) in relation to the locations of public water pumps. Tufte says, "Snow observed that cholera occurred almost entirely among those who lived near (and drank from) the Broad Street water pump. He had the handle of the contaminated pump removed, ending the neighborhood epidemic which had taken more than 500 lives."

Our Early Medical Maps page describes two other early examples of epidemiological maps, from Arthur H. Robinson's, Early Thematic Mapping in the History of Cartography: Snow's (1855) map showing the areas served by two water companies, and Perry's (1844) map of incidence of an epidemic in Glasgow (darker shading means greater incidence). John Snow (1813 - 1858) was also the first physician to practice full-time as an anesthetist. See also The Virtual Museum of Anesthesiology: John Snow