The most common conditions in rapidly growing cities were infectious diseases spread by contaminated water, overcrowding, and poor sanitation. Cholera, typhoid fever, tuberculosis, and gastrointestinal illnesses killed city residents at staggering rates during the 18th and 19th centuries, when industrialization drew millions of people into urban centers that lacked basic infrastructure to support them.
Why Cities Were So Dangerous
Industrialization triggered massive population shifts into cities across Europe and North America. London, New York, and other major centers swelled with workers, but housing, water systems, and waste disposal didn’t keep pace. Poor neighborhoods were packed with families in cramped quarters served by inadequate or nonexistent public water supplies. In London, the introduction of sewers and flushing toilets that drained directly into the Thames turned the river into an open sewer, with tides pushing contaminated water back upstream.
The consequences were severe. In the largest American cities around 1860, life expectancy at birth was roughly 27 years, compared to nearly 47 years for people living in rural areas. In Massachusetts towns with populations over 10,000 in 1830, life expectancy at ages 10 to 14 was about 46.7 years. In towns with fewer than 1,000 people, it was 52.5 years. As late as 1901, white males born in rural parts of the United States could expect to live a full decade longer than those born in cities. The bigger the city, the worse your odds.
Cholera and Contaminated Water
Cholera was one of the most feared diseases in 19th-century cities. It struck in devastating waves: England experienced major epidemics in 1831, 1848, 1854, and 1866. The disease spreads through water contaminated with human waste, and rapidly growing cities created the perfect conditions for it. Pipes leaked, sewage flowed into the same rivers that supplied drinking water, and thousands of people shared the same compromised sources.
The breakthrough came in 1854, when John Snow investigated a cholera outbreak in London’s Soho district. He traced the epidemic to a single contaminated water pump on Broad Street and had the pump handle removed, helping end the outbreak. He further compared households receiving water from two different supply companies: one drawing from a sewage-contaminated section of the Thames, the other from an upstream, cleaner part of the river. Infection rates were dramatically higher among those drinking the contaminated water. Snow’s work reinforced the push for sewage drainage and water purification systems that would eventually bring cholera under control.
Typhoid Fever and Open Sewers
Typhoid fever followed a similar path of transmission. The bacteria responsible spread when a dense population’s waste found its way back into their water supply. In many cities, water pipes ran through ground heavily contaminated with human feces. When water service was intermittent and pressure dropped inside the pipes, contaminated material from the surrounding soil seeped in through cracks and breaks. This created what researchers have described as a remarkably efficient man-made pathway for spreading disease through an entire community.
In some areas, untreated human waste was also used to fertilize crops, extending the chain of infection beyond the city’s water pipes. Typhoid was ultimately controlled in North American and European cities only through the construction of centralized water treatment and wastewater systems in the late 19th and early 20th centuries.
Tuberculosis and Overcrowding
While cholera and typhoid traveled through water, tuberculosis spread through the air. It thrived in the overcrowded tenements and factories of growing cities, where people lived and worked in tight quarters with poor ventilation. Reduced personal space and frequent close contact made person-to-person transmission far easier. Population density is one of the strongest predictors of tuberculosis rates: modern research from China found that higher population density was associated with significantly increased tuberculosis incidence, even after adjusting for other factors.
Unlike the waterborne diseases that struck in sudden epidemics, tuberculosis was a slow, chronic killer. It was a constant presence in city life for decades, and its control required not just medical advances but improvements in housing and living conditions.
Scarlet Fever and Child Mortality
Children bore the heaviest burden of disease in growing cities. By 1900, up to 30% of infants in some U.S. cities died before their first birthday. Scarlet fever was the leading cause of death among children aged one to nine in England during the 1850s and 1860s, accounting for much of the unusually high childhood mortality that characterized this period. A surge in scarlet fever virulence between roughly 1830 and 1870 coincided with the peak of urban overcrowding, making it one of the defining diseases of the era. Gastrointestinal diseases, spread by the same unsanitary conditions that fueled cholera and typhoid, also killed enormous numbers of young children.
Bad Air Theory Delayed Real Solutions
For much of the 19th century, most doctors and officials believed diseases were caused by “miasma,” foul-smelling air rising from rotting organic matter. This theory wasn’t entirely useless, since it motivated cleaning up filthy streets, but it directed attention away from the real culprits: contaminated water and person-to-person transmission. The germ theory of disease, which identified specific microorganisms as the cause of specific illnesses, gained solid scientific support primarily in the 1880s but didn’t fully replace miasma theory in the minds of physicians until the final years of the century.
The practical result was that sanitary reform moved forward under both theories simultaneously. Whether officials believed they were clearing bad air or eliminating germs, the interventions overlapped: better sewage systems, cleaner water, and improved waste removal.
How Cities Finally Got Healthier
The turning point came through public infrastructure, not medicine. Britain’s Public Health Act of 1848 was one of the earliest comprehensive responses, covering poverty, housing, water supply, sewerage, environmental conditions, and food safety. It established that because problems like contaminated water and open sewage affected entire populations, the responsibility for fixing them belonged to local and national government. Officials called “inspectors of nuisances” were appointed to identify and address hazards.
Over the following decades, cities across Europe and North America built centralized water treatment plants, enclosed sewer systems, and waste disposal infrastructure. These changes vastly reduced the threat of cholera, typhoid, and many other waterborne diseases. The pattern is clear in hindsight: the conditions common to rapidly growing cities weren’t inevitable features of urban life. They were the result of population growth outpacing the systems meant to keep people alive. Once those systems caught up, city living became dramatically safer.