John Snow has become a legendary figure partly for his use of spatial data to support his once controversial theory that cholera is a water-borne disease. For his study of London south of the Thames, Snow used data compiled by William Farr for the Registrar General during the 1853–4 epidemic. Using a larger data set compiled by William Farr in 1868, we use geographical information system-based software ArcGIS to spatially illustrate the cholera mortality rate in London subdistricts during the Asiatic cholera epidemics of 1848–9, 1853–4, and 1866. We then map the waterfields of London's eight water companies allowing us to highlight the connection John Snow saw between the rate of cholera mortality within a subdistrict and which water company operated within that particular subdistrict. Our maps also show the connection between the rate of cholera mortality in each subdistrict and average subdistrict elevation, a variable which Farr initially believed was more significant than water source.

Nicola Tynan is a professor of Economics at Dickinson College.

Published as: Cicak, Tessa and Nicola Tynan. Mapping London's Water Companies and Cholera Deaths. The London Journal 41, no. 1 (2015): 21-32. This author post-print is made available on Dickinson Scholar with the permission of the publisher. For more information on the published version, visit Taylor and Francis's Website.