As economic, political, and cultural centers, cities are at the heart of most contemporary societies, as they have been for millennia. In spite of the Cassandras who periodically lament their demise or imminent death, cities have a way of coming back from their low points--of surviving economic crises, outmigration, and vexing social dilemmas. Today, many large US cities once thought to be dying have rebounded not only because of economic restructuring...