The rural portion of an extended city may consist of several separate pieces of territory, provided that each piece is at least 5 square miles in size and has a density less than 100 people per square mile. The urban portion of an extended city consists of territory that has a density of at least 100 people per square mile. Along with jumps, nonresidential urban land use, and undevelopable territory, extended cities are another instance where portions of the UA can have a density less than 1,000 people per square mile.
The criteria for jumps, indentations, and enclaves also apply within extended cities, except that the density thresholds are lower—50 and 100 people per square mile for qualifying blocks instead of 500 and 1,000 people per square mile. If the extended city has low-density exclaves that are adjacent to its rural portions, these exclaves become part of the rural portion.
There is no minimum total population for UA extended cities; however, non-UA extended cities must have at least 2,500 inhabitants. Before the 1990 census, the Census Bureau defined extended cities only for incorporated places inside UAs. The delineation of non-UA extended cities provides better population density statistics for the Nation’s urban population by excluding those portions of incorporated places that contain vast expanses of empty or near-empty land. (Refer to Table 9-2 in Chapter 9, “Places.”)
All candidate or potential UAs that have a 1990 census population of 50,000 or more qualify as UAs and appear in the 1990 census data presentations. Those potential areas that have a 1990 population below 50,000 fail to achieve urbanized status; however, their incorporated places and/or CDPs are considered non-UA urban places if they have at least 2,500 inhabitants.
The Census Bureau never creates a new UA from the territory of an existing UA, nor does it ever transfer large portions of populated territory from one UA to another. Where two or more UAs are contiguous, the Census Bureau decides whether to maintain separate UAs or to merge them into a single
Urban and Rural Classifications12-11
