If “suburb” means an urban margin that grows more rapidly than its already developed interior, the process of suburbanization began during the emergence of the industrial city in the second quarter of the nineteenth century. Before that period the city was a small highly compact cluster in which people moved about on foot and goods were conveyed by horse and cart. But the early factories built in the 1830's and 1840's were located along waterways and near railheads at the edges of cities, and housing was needed for the thousands of people drawn by the prospect of employment. In time, the factories were surrounded by proliferating mill towns of apartments and row houses that abutted the older, main cities. As a defense against this encroachment and to enlarge their tax bases, the cities appropriated their industrial neighbors. In 1854, for example, the city of Philadelphia annexed most of Philadelphia County. Similar municipal maneuvers took place in Chicago and in New York. Indeed, most great cities of the United States achieved such status only by incorporating the communities along their borders.
With the acceleration of industrial growth came acute urban crowding and accompanying social stress conditions that began to approach disastrous proportions when, in 1888, the first commercially successful electric traction line was developed. Within a few years the horse-drawn trolleys were retired and electric streetcar networks crisscrossed and connected every major urban area, fostering a wave of suburbanization that transformed the compact industrial city into a dispersed metropolis. This first phase of mass-scale suburbanization was reinforced by the simultaneous emergence of the urban Middle class whose desires for homeownership in neighborhoods far from the aging inner city were satisfied by the developers of single-family housing tracts.

In 1860 the United States was predominantly rural. Most people were engaged in agriculture, and about 80 percent of the population actually resided on farms or in small villages. Only 20 percent lived in towns and cities of 2,500 or more, the census definition of an urban area after 1880. New York alone in 1860 had more than 1 million people, and only 8 cities could boast about a population of more than 100,000. Thereafter the transition from a rural to a predominantly urban nation was especially remarkable because of its speed. By 1900, urbanization, with all of its benefits, problems, and prospects for a fuller life, became the mark of modern America.
The changing physical landscape reflected the shift to an urbanized society. Railroad terminals, factories, skyscrapers, apartment houses, streetcars, electric engines, department stores, and the increased pace of life were all signs of an emerging urban America. Indeed, the vitality, dynamic quality, variety, and restless experimentalism in society centered in the urban communities where the only constant factor was change itself.
Urbanization did not proceed uniformly throughout the nation. New England and the Middle Atlantic states contained the highest percentage of city dwellers. In the Middle West, the growth of cities such as Chicago, Milwaukee, Cleveland, and St. Louis showed the importance of urbanization in that region. The three West Coast states also experienced rapid urban growth. In the South, urbanization developed much more slowly, although by 1910 the expansion of transportation, commerce, and industry had greatly increased the population of older cities such as New Orleans and stimulated the growth of new urban centers such as Birmingham. However, the South remained predominantly rural. Only somewhat more than 20 percent of the population in that region was urban by 1910.
In some regions the urban impact had a depressing effect upon the surrounding rural communities. Much of New England in the late nineteenth century presented a discouraging picture of abandoned farms and sickly villages as people forsook the countryside and rushed to the larger towns and cities. In the Middle West, particularly Ohio and Illinois, hundreds of townships lost population in the 1880's.