This is a book about the future of metropolitan areas in the United States. The current state of technology and the existing pattern of land use will determine much of that future over the next few decades. To illustrate this point, consider the prosaic yet easily overlooked fact that all of the adults who will be alive in the next twenty years have already been born. Therefore, it is first necessary to understand the present and the past before looking directly at the future.

Consider housing, for example. Approximately 2 percent of the housing stock in the United States consists of new construction each year. Put another way, more than 80 percent of the housing stock is more than ten years old. The decaying manufacturing districts, public housing projects, and office blocks in some central cities were once brand-new construction. The new construction today is the old building of tomorrow, and the options available to us are restricted by our choices today and in the past.