How did Detroit and Pittsburgh grow geographically despite population declines between 1970 and 1990?

Between 1970 and 1990, cities like Detroit and Pittsburgh experienced geographic expansion—often referred to as urban sprawl—despite concurrent population declines. This phenomenon was driven by a combination of lifestyle preferences and infrastructure development rather than population growth.

Many residents sought increased living space and residential amenities that were more readily available and affordable in suburban areas compared to inner-city dwellings. This migration was facilitated by the widespread availability of the private automobile and the expansion of the Interstate Highway System, which made previously inaccessible land viable for new home construction.

While some individuals moved to suburbs to enjoy a lifestyle closer to nature, others were motivated by a desire to escape the congestion, crime, and noise of the city. Consequently, even as the core populations of these metropolitan areas decreased, the physical footprint of the cities grew by approximately 30 percent during this period as development pushed outward into lower-density residential areas.1