Clean urban water, distributed and collected through centralized regional infrastructure, is a driving force in development of the rapidly growing metropolitan regions of the arid Southwest. This study examines the internal magnitude and location of water infrastructure in the city of Phoenix, Arizona, from 1953 to 2003. Regional building-permit data were the basis for identifying six cycles of boom-and-bust real estate activity. Using Water Services Department GIS files, we find that the grid of 1-mile arterial streets provided a systematic framework for incremental water infrastructure expansion. Over this 50-year period, the water system consolidated existing settlements with private water sources and aggressively provided revenue-generating services to an expanding customer base. By 1994–2003, however, new urban fringe development existed only at the northern and southwestern boundaries of this extensive central city. Water infrastructure activities now increasingly included replacement for intensified service, renovation, maintenance, and repair. Detailed analyses of this and other urban water systems provide an additional source of broad insights into processes of both external fringe development and internal land intensification.