Using the urbanized area that spreads across northern New Jersey and around New York City as a case study, this book presents a convincing explanation of metropolitan fragmentation—the process by which suburban communities remain as is or break off and form separate political entities. The process has important and deleterious consequences for a range of urban issues, including the weakening of public finance and school integration. The explanation centers on the independent effect of urban infrastructure, specifically sewers, roads, waterworks, gas, and electricity networks. The book argues that the development of such infrastructure in the late nineteenth century not only permitted cities to expand by annexing adjacent municipalities, but also further enhanced the ability of these suburban entities to remain or break away and form independent municipalities. The process was crucial in creating a proliferation of municipalities within metropolitan regions. The book thus shows that the roots of the urban crisis can be found in the interplay between technology, politics, and public works in the American city.