A closer look
When the Great Plague of London struck in 1665, most people fled the city while cats and dogs were slaughtered out of fear they spread the disease. Ironically, those animals were predators of the real carriers—rats and their fleas. But the chaos left something enduring: the birth of the modern city registry. Officials tracking deaths began recording population data street by street, creating the precursor to urban statistics. It was tragedy’s awkward child: from fear of contagion came the numbers that allow us to plan sanitation and housing today. The plague made data fashionable, marrying memory and measurement in one grim notebook.
