Many think of the Victorian era as a time of tight-laced corsets and formal teas. And it was—but it was also the time of the Great Stink, a two-month stretch of 1858 in which London's primary water source, the River Thames, was so full of untreated sewage baking in the sun that the entire city took on an odious reek. The smell was so bad that it was blamed for illnesses among the upper class, reportedly caused citizens miles away to throw up whenever the wind changed, and eventually lead to the development of the London sewage system.
London didn't grow into a city overnight, and the Great Stink of 1858 didn't happen overnight either. Centuries of dumping raw human, animal, and industrial waste directly into the river to be carried out to sea left the city a rancid, unhealthy mess. It was the ingenuity and work of a few people that finally ended London's Great Stink, improving the health, air quality, and hygiene for the millions of people who have lived in London since then.
London's sewer systems were in terrible condition prior to the Great Stink in 1858. Cesspits, large tanks or sometimes just holes in the ground filled with raw sewage, were designed to overflow into the streets when they were full via crude culverts that led to trenches down major thoroughfares. Often, the waste from these pits would seep into the foundations and basements of homes, sometimes causing explosions when too much methane became trapped. The waste that did make it into the sewer system was funneled straight to the Thames and other clean water sources, which likely led to cholera outbreaks in 1832, 1849, and 1854 that killed thousands of Londoners.
From the 1600's on, the city of London didn't worry much about funneling their excrement into the Thames because they believed that the river would carry all of their human, animal, and industrial waste out to sea, making it somebody else's problem. In reality, part of the Thames is a tideway, meaning it's affected by the tides—any sewage or other waste that made its way into the river could be carried back and forth along the river, not just in one direction. Centuries of waste moving back and forth through the river left the river full of actual crap, and during the heat wave of 1858, that waste came to the surface.
Because of the rise in population, the increased amount of waste pouring into the Thames, and the lack of cleanup effort, the river was in a horrific state by 1858. The city had grown with no meaningful changes to its sewer system, and the Thames was the city's main source of drinking water. With hundreds of years of garbage, human and industrial waste polluting it, the river was thick, brown, and opaque. Scientist Sir Michael Faraday warned the public of this in 1855, writing, "if we neglect this subject [then] a hot season [will] give us sad proof of the folly of our carelessness," which proved true during The Great Stink three years later.
With centuries worth of waste built up in the Thames, as Michael Faraday predicted, it was only a matter of time before the situation would demand attention. That came in June of 1858, when a heat wave in London made it impossible to ignore the sewage any longer. An extended dry spell made the river slow nearly to a stop, and the summer heat began to cook the fetid waters.
The smell that emerged consumed the city of London. Prime Minister Benjamin Disraeli called the river "a stygian pool reeking with ineffable and unbearable horror." Reports said that miles away, townsfolk would be moved to vomit any time the wind changed. The smell was so terrible that it forced Parliament to take action, drenching their curtains in chloride of lime to quell the stink. When not even that worked, the path forward was clear—something would need to be done about the reeking river.