Cholera 1849: Low Ground, Bad Water and a Long Shadow in London

In 1849 cholera killed 14,007 people in the 38 registration districts of London that William Farr tabulated in his 1852 report. Farr found that mortality fell steadily with height above the Thames and read the pattern as evidence for a miasmatic cause; John Snow argued that cholera was carried in drinking water. I revisit both arguments with openly available transcriptions of their own tables. Across Farr's districts the rank correlation between height and the death rate is -0.81, but height and water supply are closely entangled: the twelve districts drinking Thames water drawn between Battersea and Waterloo Bridge lie at most 22 feet above high water and lost 114.4 people per 10,000, against 17.8 in districts supplied from the Thames at Kew and Hammersmith. Height and water source each explain about three-fifths of the variation in logged death rates, and together 75%. The decisive comparison is in south London, where houses supplied by the Lambeth and the Southwark and Vauxhall companies died at the same rate in 1848 to 1849 (12.2 per 1,000) but at 3.6 and 13.5 per 1,000 in 1853 to 1854. On Snow's 1854 Broad Street map, half of the 578 deaths lay within 117 metres of the pump. Finally, I link the 1849 districts approximately to 353 present-day small areas: the 1849 death rate bears no relation to household income in 2023 (rank correlation -0.07), while the 1849 value of housing per person does (0.46). Cholera's map has faded; the map of wealth has not. Data files derived from HistData and the cholera R package are GPL, files from SnowCholera are BSD 2-Clause, and files derived from ONS and Ordnance Survey data are under the Open Government Licence v3.0. Code is MIT. Interactive version: https://tristan-hotham.github.io/cholera-1849/. Data and code: https://github.com/Tristan-Hotham/cholera-1849. Blog post: https://blog.tristanhotham.com/2026/10/27/cholera-1849/.