A new form of human settlement has emerged in the twentieth century, radically different from the cities of the past. The city has become a city-region. American city-regions' population growth is now dramatically outpaced by their geographic growth. In the two decades from 1970 to 1990, the New York region had a modest population increase of 8 percent, but it had an explosive growth of 65 percent in its built-up urbanized land. While Chicago grew 4 percent in population, its urbanized land increased 46 percent. Even places that were declining in their population were simultaneously growing in their urban area; Cleveland, for example, had a population decline of 8 percent, while it expanded geographically by 33 percent. This urban growth cycle is similar across America. City-regions are exploding into their surrounding countryside at growth rates that are eight to ten times greater than their population increases. What is new is not the size of cities, but a change in their form. New...