By serving travelers and commerce, roads and streets unite people and foster economic growth. But as they develop, roads and streets also disrupt old patterns, upset balances of power, and isolate some as they serve others. The consequent disagreements leave historical records documenting social struggles that might otherwise be overlooked. For long-distance travel in America before the middle of the 20th century, roads were generally poor alternatives, resorted to when superior means of travel, such as river and coastal vessels, canal boats, or railroads were unavailable. Most roads were unpaved, unmarked, and vulnerable to the effects of weather. Before the railroads, for travelers willing to pay the toll, rare turnpikes and plank roads could be much better. Even in towns, unpaved streets were common until the late 19th century, and persisted into the 20th. In the late 19th century, rapid urban growth, rural free delivery of the mails, and finally the proliferation of electric railways and bicycling contributed to growing pressure for better roads and streets. After 1910, the spread of the automobile accelerated the trend, but only with great controversy, especially in cities. Partly in response to the controversy, advocates of the automobile organized to promote state and county motor highways funded substantially by gasoline taxes; such roads were intended primarily for motor vehicles. In the 1950s, massive federal funds accelerated the trend; by then, motor vehicles were the primary transportation mode for both long and short distances. The consequences have been controversial, and alternatives have been attracting growing interest.
As places of dense habitation, cities have always required coordination and planning. City planning has involved the design and construction of large-scale infrastructure projects to provide basic necessities such as a water supply and drainage. By the 1850s, immigration and industrialization were fueling the rise of big cities, creating immense, collective problems of epidemics, slums, pollution, gridlock, and crime. From the 1850s to the 1900s, both local governments and utility companies responded to this explosive physical and demographic growth by constructing a “networked city” of modern technologies such as gaslight, telephones, and electricity. Building the urban environment also became a wellspring of innovation in science, medicine, and administration. In 1909–1910, a revolutionary idea—comprehensive city planning—opened a new era of professionalization and institutionalization in the planning departments of city halls and universities. Over the next thirty-five years, however, wars and depression limited their influence. From 1945 to 1965, in contrast, represents the golden age of formal planning. During this unprecedented period of peace and prosperity, academically trained experts played central roles in the modernization of the inner cities and the sprawl of the suburbs. But the planners’ clean-sweep approach to urban renewal and the massive destruction caused by highway construction provoked a revolt of the grassroots. Beginning in the Watts district of Los Angeles in 1965, mass uprisings escalated over the next three years into a national crisis of social disorder, racial and ethnic inequality, and environmental injustice. The postwar consensus of theory and practice was shattered, replaced by a fragmented profession ranging from defenders of top-down systems of computer-generated simulations to proponents of advocacy planning from the bottom up. Since the late 1980s, the ascendency of public-private partnerships in building the urban environment has favored the planners promoting systems approaches, who promise a future of high-tech “smart cities” under their complete control.