September 7, 1854: The St. James Board of Governors and Directors of the Poor was convinced by Dr. John Snow that the Broad Street pump was the source of a cholera epidemic in a London neighborhood. The Board ordered the removal of the pump handle preventing a continuation of the epidemic. Incredibly, public protests resulted in the replacement of the pump handle on September 26, 1855. The Broad Street well was not permanently taken out of service until the cholera epidemic of 1866.
Reference: Vinten-Johansen, Peter, Howard Brody, Nigel Paneth, Stephen Rachman and Michael Rip. Cholera, Chloroform, and the Science of Medicine. New York:Oxford University, 2003, 292-4, 310, 316-317.