Two of the most influential urban medical maps of the 19th century were those in Dr John Snow’s essay On the mode of communication of cholera, 2nd edition, 1855. Snow was convinced that cholera was carried by contaminated water, and his report contained a map accompanied by statistical tables setting out the death rates in the areas served, respectively, by the Southwark & Vauxhall Water Company and the Lambeth Water Company. In 1852 the Lambeth Company had changed its source of supply to Thames Ditton, which was free of pollution from London sewage. In the red-shaded areas served exclusively by the Lambeth Company, there were only five deaths per 1000 households. While the blue-shaded Southwark & Vauxhall Company’s areas, served by water from the Thames at London Bridge, had a mortality rate of 71 deaths per 1000.
This is an extract from James Elliot’s chapter ‘Medical and social mapping’ first published in Elliot’s The City in Maps (British Library: London, 1987), pp. 78–81.