John Snow removed the handle of the Broad Street pump in 1854. The action took place on 8 September during a severe cholera outbreak in Soho, London, after Snow mapped deaths and found that cases clustered around people who drank from the pump.
Snow opposed the prevailing miasma theory, which blamed cholera on poisonous air. He argued instead that contaminated water carried the disease, although the bacterial cause, Vibrio cholerae, was not yet understood. A leaking cesspit near the well is now believed to have contaminated the water with fecal matter.
The pump-handle story is often simplified into a moment that immediately ended the epidemic. In reality, cases were already declining and many residents had fled the area, so removing the handle was not conclusive proof by itself. Its importance was methodological: Snow combined interviews, geographic mapping, and mortality data to challenge accepted medical opinion.
The pump was later restored, and a replica now commemorates the investigation on Broadwick Street, the modern name of Broad Street. Snow’s work helped establish epidemiology and influenced later urban sanitation reforms.