Defining rural areas: U.S. Census uses small geographic units (blocks) to define urban/rural
One definition of rural, based on relatively small geographic building blocks, is provided by the U.S. Census Bureau in its urban-rural classification system. In this delineation, rural areas comprise open country and settlements with fewer than 2,500 residents. Urban areas comprise larger places and the densely settled areas around them, but do not necessarily follow municipal boundaries. Urban areas are essentially densely settled territory as it might appear from the air.
Download higher resolution chart (4267 pixels by 3417, 300 dpi)