The Forces Behind Urban Growth
One force behind urban growth was simply national population growth. The U.S. rate of natural increase (births minus deaths) was extremely rapid and was augmented by immigration, particularly after the inauguration of transatlantic steam service in the 1840s. But these facts do not answer the question of why urban growth proceeded so much more rapidly than did total population growth.
Part of the explanation was a side effect of the industrial revolution. As agricultural machinery made farmers more productive, workers were freed to take on other employment, much of it in the cities. In 1800 perhaps 85 to 90 percent of the U.S. labor force was engaged in farming. By 1880 that figure was down to about 50 percent.
Another consequence of the industrial revolution was the shift from cottage industries to factory production, creating the need for mass labor forces at specific points. That, in turn, created the need for massed housing nearby. The growth of large-scale manufacturing also brought into being the modern corporation, with a large administrative force concentrated at a single point. Finally, factory production and the enormous increase in consumer goods it created brought into being the department store, which also concentrated a large labor force at a single point.
The growth of large cities was also promoted by the development of low-cost transportation. The coming of railroad and steamboat technology around 1830 gave cities a long reach into their hinterlands to obtain raw materials and agricultural products and also to market the products they produced. In the absence of such transportation, cities would necessarily be small, since the market areas that sustained their commercial and manufacturing sectors would have been small.
The rapid settling of the country and the opening of new lands demanded the creation in short order of a system of cities to perform the commercial and manufacturing processes that the new industrial technology was making possible. Writing in 1899, Adna Weber noted,
In a new country the rapid growth of cities is both natural and necessary, for no efficient industrial organization of a new settlement is possible without industrial centers to carry on the necessary work of assembling and distributing goods. A Mississippi Valley empire rising suddenly into being without its Chicago and its smaller centers of distribution is almost inconceivable to the nineteenth-century economist. That America is the "land of mushroom cities" is therefore not at all surprising.2
Although the four forces noted—population growth, increased agricultural productivity, factory production, and low-cost transportation—are sufficient to explain the rapid growth of urban populations, they do not entirely explain the form of nineteenth-century cities.