Possibly one of the best known historical maps today, Dr. John Snow‘s map traced cholera deaths to their water pump source.

In this talk, Steven Johnson brings the summer of 1854 to life as he describes the events chronicled in his 2006 book “The ghost map : the story of London’s most terrifying epidemic–and how it changed science, cities, and the modern world”

Due to the Industrial Revolution, the population of London had grown tremendously.  What had not grown was sanitary infrastructure.  With cess pools in the basements, plus cows in the attics and horses on the streets, the waste kept piling up.  Eventually it was dumped into the Thames…  As Johnson says, “It was an amazingly smelly city”.

So, when Cholera epidemics occurred, it was thought to be caused by the stinky air.  Dr. Snow believed Cholera to be water born.  He created the map to trace the location of deaths of those who drank from a specific water pump.  While the map was an important step, it still took several years for London to create city wide sewers, due to disbelief in germ theory and cost.

Johnson believes this incident provided the basis for the rise of the modern world.

For more links, please see this WindRose post under Maps to Know:

1854 / Cholera Map / Dr. John Snow