In 1854 an outbreak of cholera struck Soho, a residential district in London, England, killing entire families within days. At the time, not much was known about cholera and how it spread. After hearing of the outbreak, one hopeful epidemiologist, by the name of John Snow, set out to prove his theory that cholera spread through contaminated water. Dr. Snow mapped out the various water sources throughout the neighborhood along with the known deaths in the neighborhood. It didn’t take long before Dr. Snow had located the source of the outbreak. The majority of the deaths were centered around one particular water pump that was rumored to have “the best water in town.” After examining the water for cholera, Snow had the pump removed and the outbreak came to a stop. Snow’s theory was right; he not only changed what we know about cholera today but also innovated how we use maps today.

Image Credit: University of Delaware.