Defining rural areas: U.S. Census uses small geographic units (blocks) to define urban/rural

One definition of rural, based on relatively small geographic units, 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 5,000 residents and fewer than 2,000 housing units. 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.