The Age of Progress: Science, Medicine, and the City

For centuries doctors blamed disease on miasma, foul air rising from filth and decay, so the fix was ventilation and general cleanliness. In the 1860s and 1870s Louis Pasteur showed that specific microorganisms caused specific diseases, and Robert Koch developed methods to isolate the exact bacterium behind a given illness. That precision mattered: once a doctor could name the organism, he could target it, with sterilized instruments, antiseptics on wounds, and eventually vaccines. Joseph Lister applied this directly to surgery, washing hands, tools, and wounds to kill germs, which is why a surgery patient who would have died of infection in 1850 was likely to live by 1880. The same logic reshaped public health, since clean water and sewage systems now stopped identifiable pathogens, not just bad smells.

These medical gains show up in the numbers. European life expectancy at birth sat around 30 to 35 years in 1800, barely changed from centuries before, then climbed toward 45 to 50 years by 1914. The jump concentrates in the second half of the century, once germ theory, sanitation, and vaccination campaigns took hold together, rather than any single breakthrough acting alone.

Cities themselves were rebuilt to match. Baron Haussmann tore wide, straight boulevards through Paris's cramped medieval core starting in the 1850s, improving traffic flow, sunlight, and sewage drainage, and incidentally making barricades harder to build during unrest. Wider streets and longer lives created room for a new public culture: department stores sold mass-produced goods to a growing middle class, cheap newspapers reached readers citywide, and spectator sports gave strangers in a crowded city something shared to cheer for.