Snow's map

Snow's map is a historic diagram created by John Snow in 1854 to illustrate the spread of cholera cases in London. It plots locations of individual cholera deaths and marks a common water source—a contaminated pump on Broad Street. The map reveals clusters of cases near the pump, suggesting a link between the water source and the disease. Snow’s work was foundational in understanding disease transmission through contaminated water, marking a significant step in public health and epidemiology by illustrating how environmental factors contribute to disease spread.