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The Industrial Revolution led to the rapid growth of cities in the northeastern states because in this region were located the big factories and fabrics that introduced mass production as their form to produce goods. We are talking about cities such as New York City and Chicago, among others.
Many people from the south. who lived in the rural areas of that region, decided to move to the larger cities of the northeast precisely to get a job in the fabrics. Many immigrants came to the United States to work in factories, They came from Europe and Asia. They went to New York or Chicago, and many other cities.
These workers labored under difficult and unhealthy conditions. They worked long hours and received a low salary.
Of course, the population grew and these workers, as they were poor, they had to live in poor overcrowded spaces with no ventilation at all and where disease spread quickly and easily.