John Snow's Cholera Map

Snow, John. On the mode of communication of cholera. John Churchill, New Burlington Street: London, [1855].

English physician John Snow (1813-1858) suspected that contaminated water was to blame for a cholera outbreak in London in the 19th century. Snow investigated each case and noted which water pump the infected individual used. He marked the cases on a map published in this 1855 edition of On the mode of communication of cholera. His map details the spread of cholera in the Soho area of London, showing a concentration of cases around the contaminated Broad Street pump. His data was convincing enough to have the water pump at the center of the outbreak disabled which led to the end of the epidemic.