A census-designated place (CDP) is a type of place (a concentration of population) identified by the United States Census Bureau for statistical purposes. CDPs are delineated for each decennial census as the statistical counterparts of incorporated places such as cities, towns and villages. CDPs are communities that lack separate municipal government, but which otherwise physically resemble incorporated places. CDPs are delineated solely to provide data for settled concentrations of population that are identifiable by name but are not legally incorporated under the laws of the state in which they are located. The boundaries of a CDP have no legal status. The U.S. Census bureau states that census-designated places are not considered to be incorporated places, and that it includes census-designated places in Hawaii in its city population lists because of Hawaii's municipal structure. In addition census city lists from 2007 include Arlington County, Virginia's CDP in the list with the incorporated places.
The Census Bureau reported data for some unincorporated places as early as the 1850 Census, though usage continued to evolve through the 1890 Census, in which, for the first time, the Census mixed unincorporated places with incorporated places in its products with "town" as its label. This made it confusing to determine which of the "towns" were or were not incorporated.
The 1900 through 1930 Censuses did not report data for unincorporated places.
For the 1940 Census, the Census Bureau compiled a separate report of unofficial, unincorporated communities of 500 or more people. The Census Bureau officially defined this category as "unincorporated places" in the 1950 Census. For the 1950 Census, these types of places were identified only outside urbanized areas. In 1960, the Census Bureau also identified unincorporated places inside urbanized areas, but with a population of at least 10,000. For the 1970 Census, the population threshold for "unincorporated places" in urbanized areas was reduced to 5,000. For the 1980 Census, the designation was changed to "census-designated places". For the 1990 Census, the population threshold for CDPs in urbanized areas was reduced to 2,500. From 1950 through 1990, the Census Bureau specified other population requirements for unincorporated places or CDPs in Alaska, Puerto Rico, island areas, and Native American reservations. Minimum population criteria for CDPs were dropped with the 2000 Census.The Census Bureau's Participant Statistical Areas Program (PSAP) allows designated participants to review and suggest modifications to the boundaries for CDPs. The PSAP will be offered to county and municipal planning agencies during 2008.
The boundaries of such places may be defined in cooperation with local or tribal officials, but are not fixed, and do not affect the status of local government or incorporation; the territories thus defined are strictly statistical entities. CDP boundaries may change from one census to the next to reflect changes in settlement patterns. Further, as statistical entities, the boundaries of the CDP may not correspond with local understanding of the area with the same name. Recognized communities may be divided into two or more CDPs while on the other hand, two or more communities may be combined into one CDP. A CDP may also cover the unincorporated part of a named community where the rest lies within an incorporated place.
By defining an area as a CDP, that locality then appears in the same category of census data as incorporated places. This distinguishes CDPs from other census classifications, such as minor civil divisions (MCDs), which are in a separate category.
The population and demographics of the CDP district are included in the data of county subdivisions containing the CDP. In no case is a CDP defined within the boundaries of what the Census Bureau regards to be an incorporated city, village or borough. However, the Census Bureau considers towns in New England states and New York as well as townships in some other states as MCDs, even though they are incorporated municipalities in those states.
There are a number of reasons for the CDP designation: