American cities expanded during the late 19th century, as industrial growth was fueled by the arrival of millions of immigrants and migrants. Poverty rates escalated, overwhelming existing networks of private charities. Progressive reformers created relief organizations and raised public awareness of urban poverty. The devastating effects of the Great Depression inspired greater focus on poverty from state and federal agencies. The Social Security Act, the greatest legacy of the New Deal, would provide a safety net for millions of Americans. During the postwar era of general prosperity, federal housing policies often reinforced and deepened racial and socioeconomic inequality and segregation. The 1960s War on Poverty created vital aid programs that expanded access to food, housing, and health care. These programs also prompted a rising tide of conservative backlash against perceived excesses. Fueled by such critical sentiments, the Reagan administration implemented dramatic cuts to assistance programs. Later, the Clinton administration further reformed welfare by tying aid to labor requirements. Throughout the 20th century, the urban homeless struggled to survive in hostile environments. Skid row areas housed the homeless for decades, providing shelter, food, and social interaction within districts that were rarely visited by the middle and upper classes. The loss of such spaces to urban renewal and gentrification in many cities left many of the homeless unsheltered and dislocated.
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.