If by "suburb" is meant 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. In1854, 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.

    如果"郊區"指的是比已建好的城市內部發展更為迅速的城市邊緣地帶，那么郊區化可以說始于 1825 年至 1850 年工業化城市出現期間。 

    在這之前，城市只是高度密 集的小聚居群. 在其中，人們步行走動，商品靠馬車來運送。但是建于 18 世紀三四十年代的早期工廠位于城邊的航道和鐵路附近，被工作機會吸引到這里的成千上萬的人們需要住 房.漸漸地，在與舊有的主要城區相毗鄰的地方，不斷涌現出由排房和公寓樓組成的工人 聚居區，包圍了工廠。作為對這種侵蝕的自衛，也為了擴大它們收稅的地域范圍，城市吞并 了工業化的臨近地帶，比如1854 年費城的城區就兼并了費縣的絕大部分地區。 相似的城市 化也發生在芝加哥和紐約。

    今天很多美國的大城市其實就是靠吞并它們附近的邊緣地區而變成大都會的。隨著工業化的加速發展，城市里出現了嚴重擁擠和相伴而來的社會壓力。 當1888 年第一條商業上成功的電氣化鐵軌被制造出來時，壓力開始接近危機的程度. 幾年之內，馬車就被廢棄了，電車網相互交織連接著各個重要的城區，從而形成了一種郊區化的潮 流，即密集的工業城市轉變成了分散的都市。此時城市中產階級的出現進一步加強了第一 波大規模郊區化。這些中產階級希望在遠離老舊城市的地區擁有住宅，單一家庭住宅地區 的開發者滿足了他們的愿望。