1. Edwin Chadwick’s Sanitary Map of Leeds, 1842

Chadwick Leeds Map

(via Wikimedia Commons; click for zoomable version)

This muddy-looking map is actually one of the most brilliant innovations in social science, ever. Created by British social reformer Edwin Chadwick as part of his 1842 Report on the Sanitary Condition of the Labouring Population, the map combines three different kinds of statistics: first, the most recent census data, second, the locations of the homes of those who died in 1830s cholera outbreaks, and third, the residences of people who died of respiratory diseases. The resulting map made the stark difference in disease and mortality rates between rich and poor both clear and undeniable, and helped to convince Parliament that social factors are a crucial part of public health.

  1. John Snow’s map of the 1854 Broad Street cholera outbreak

Snow Map Broad St

(via grammata.com; click for zoomable version)

Anyone who’s taken an intro to public health class knows the story of John Snow (not that one) and the Broad Street pump. Basically, science hadn’t yet figured out the connection between dumping raw sewage into drinking water and London’s recurrent cholera problem. Enter John Snow, a young physician who wasn’t afraid to get his hands dirty. Snow methodically tracked every victim of an 1854 outbreak of the devastating disease, and found that the cases clustered around one particular water pump on Broad Street. According to epidemiology legend, Snow removed the handle of the pump so that no one could drink from it, the epidemic ended, and everyone lived happily ever after.

In truth, we can’t really credit Snow with the end of this particular epidemic—it was already dying out on its own by the time Snow stole the pump handle. Also, London’s population suffered a few more cholera epidemics afterward. Still, the clarity of the Snow map helped to convince many that cholera is waterborne, not the result of bad air as previously thought. Who knows how many future lives Snow’s map saved?

  1. Florence Nightingale’s Rose Diagram, 1858

Nightingale Rose Diagram

(via Wikipedia)

She’s most famous for being a nurse, but Florence Nightingale was also a rockstar epidemiology innovator. Her brilliant Diagram of the Causes of Mortality in the Army in the East—frequently referred to as the “Rose Diagram” because of its floral shape—uses deceptively simple graphics to drive home an upsetting fact: far more British soldiers fighting in the Crimean War died of treatable diseases than died in battle or from any other cause. Patriotic Brits could accept their sons dying bravely in battle (think In Flanders Fields), but Nightingale’s Rose Diagram helped turn popular sentiment decisively in favor of the nascent public health and sanitation movement.

Partly as a result of her success using the Rose Diagram to make statistical analysis accessible to people with no head for numbers, Nightingale was elected the first-ever female member of the Royal Statistical Society the next year, in 1859. She used her fame to tirelessly campaign for sanitation improvements both in and outside Bonny Old England. Keep in mind that this was the height of the British Empire, so British citizens were scattered all over the globe—and their health and livelihood (and, more importantly, the bottom line back home) could be threatened by subpar sewer drainage in Mumbai or Capetown. With her statistical chops, Nightingale worked to prove that improved public health benefits everyone, even capitalists.

Featured image via Wikipedia