At the time of the 19th century, the United States was essentially all rural. Less than six percent of the entire population of 5 million people lived in towns that were larger than 2,500 residents. The only cities with populations larger than 25,000 people were Philadelphia and New York City. When the Mississippi Valley and the Northwest settled during the first half of the 19th century, much of the population of the United States migrated west. By the year 1850, the United States had 23 million people, with more than 30 percent of the population living in towns with more than 2,500 people. Although the majority of the population, about two-thirds, was involved with agriculture, commerce and industry had expanded greatly, causing many people to migrate to areas with those industries. The fastest-growing segment of the population was the urban segment. By 1900, New York, Chicago, and Philadelphia were home to millions of people.
The cities that started out as the largest at the turn of the century continued to enjoy the fastest rates of population expansion. By the year 1850, New York was home to more than half a million people. Philadelphia, Boston, New Orleans, and Charleston had large populations, as well, in the range of hundreds of thousands of people. Southern cities did not attract quite as many people as the cities to the north. It was around this time that cities began to expand in radius, going from less than one mile up to four or five miles. Northern cities began to shape into suburbs, with well defined business districts, and residential areas that were segregated socially and ethnically.
Southern cities grew in a different fashion, with populations settling toward the outskirts of the city, growing inward once the perimeter had been well settled. The cities grew as plantation owners and farmers started to migrate toward the city for the social and cultural benefits the cities offered. Cities near the coastal waters and on the riverways saw an influx in traders and bargemen in their population. The rural small towns of the South had little to offer besides self-sustaining plantations, a doctor, a small store or two, and as a result often appeared run down to visitors who were only familiar with life in the city.
Immigration from other countries and internal population migration pushed the limits of the cities in the United States during this time. Poverty, disease, and crime increased in the slum districts of the Northern cities, with immigrants banding together with people from their own countries. Antebellum immigration peaked between 1845 and 1855. In that ten-year span, more than 3 million immigrants entered the country. This was ten times the number of people that had come to America in its founding
At this time, there were three major countries from which the immigrants came. These were Ireland, Germany, and Great Britain. Those three countries alone provided nearly 85 percent of the immigrant population up to the beginning of the Civil War.
New technology, such as the invention of elevators in the 1870s, helped cities grow upward and outward with less trouble. The new iron and steel construction meant contractors could build taller buildings to accommodate all of the residential and business growth. By the 1890s, cities had clearly developed central business districts and large, imposing skylines. Cities became more than the center for business, banking, and trade, but also were central of all aspects of American culture, recreation, and social activity.
With such growth and development, cities also became a central part of social problems. Racial injustice and poverty were prominent problems in American cities. The smoke, smog, and unclean water supply made cities unhealthy places to live. Another problem of the cities of the 19th century was the growing rate of crime and corruption that came along with daily life.