U.S. Census Bureau

“ On the other hand, it is appropriate for the boundaries of geographic areas such as UAs and CDPs to change with each decennial census. Just as cities change their boundaries as they expand to provide services to, and gain jurisdiction over, additional territory, the people who live there, and the businesses that operate there, UAs and CDPs are delineated to reflect the settlement pattern at a specific moment in time. ”

“ In recent years, most boundary changes for counties have been minor and have not involved substantial shifts of population or land area. The independent cities in Virginia constitute an exception because they occasionally annex territory, as do the incorporated places in many States. Because the territory annexed by a Virginia city no longer is part of the county in which it had been located, changes in the boundaries of these independent cities also affect the boundaries of the adjacent county or counties. In other States, changes to counties occur on a piecemeal basis. ”

“ Identification of Geographic Entities In accepting or devising a new kind of geographic entity, or in maintaining those that already exist, it is important to keep the geographic concept simple enough, insofar as possible, for ready comprehension and acceptance by all members of the data user community. Easy identification and recognition are key aspects in the wide acceptance of any geographic entity for which the Census Bureau presents data in its tabulations and publications. ”

“ Each State enacts laws and regulations for establishing incorporated places. The Census Bureau designates criteria of total population size, population density, and geographic configuration for delineating CDPs. Not everyone resides in a place; in 1990, approximately 66 million people (26 percent) in the United States lived outside of any place, either in small settlements, in the open countryside, or in the densely settled fringe of large cities in areas that were built-up, but not identifiable as places. ”

“ At the time of the 1950 census—shortly after the Commonwealth legally documented the boundaries of the barrios and barrios-pueblo—a pueblo generally reflected the most densely settled part of many municipios, and also served as the historic, commercial, social, and religious center, and the seat of government of the municipio. Since 1950, when Puerto Rico’s population was about two million, urban growth has expanded beyond—in some cases far beyond—the 1947 limits of the so-called ciudades and pueblos. ”

“ Governmental unit A geographic entity established by legal action, and for the purpose of implementing administrative or governmental functions. Most governmental units have officially recognized boundaries. All area and population of the United States are part of one or more legal units, such as American Indian reservations, States, counties, county subdivisions, and incorporated places. See also active governmental unit, administrative entity, functioning governmental unit, general-purpose government, inactive governmental unit, legal entity, nonfunctioning governmental unit. ”

“ Background The decennial population censuses always have sought to identify county subdivisions as a primary geographic entity. The first census (1790) reported population counts for MCDs (towns, townships, and other units of local government) , and this practice continued throughout subsequent censuses. For States in which local governmental units did not exist below the county level, various administrative units or other area designations were used, such as companies, districts, hundreds, remainder of county, and eastern (or western) portion of county. ”

“ Since population was not viewed as having to be very equal, there was a tendency to use simple existing boundaries of familiar legal territories, such as city limits, and merely group these in convenient ways. There was also a need to define voter precincts, the finest subdivision of districts. This was not always done on a clear basis of mutually exclusive territory. Even in the 1970s, precincts in some Mississippi counties were places such as schools or fire stations, at which eligible citizens in the county could register and vote. ”

“ For instance, developing a layout of statistical entities may involve the combined use of past census data, maps, aerial photography, field observations, and information from local sources.
The functional integration principle involves the grouping together, into a single statistical area, the people, housing, or business establishments that share a central nucleus along with the surrounding, functionally related entities, such as a large city and its suburbs. Such areas tend to form a single geographic whole that operates as a cohesive functional entity or system. ”

“ Census tract boundaries normally follow visible features, but may follow governmental unit boundaries and other nonvisible features in some instances; they always nest within counties. Designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions at the time the CSAC established them, census tracts usually contain between 2,500 and 8,000 inhabitants. They may be split by any subcounty geographic entity. See also block numbering area, census statistical areas committee, census tract number, central business district. ”

“ Census blocks, the smallest geographic area for which the Bureau of the Census collects and tabulates decennial census data, are formed by streets, roads, railroads, streams and other bodies of water, other visible physical and cultural features, and the legal boundaries shown on Census Bureau maps. Census data for these areas serve as a valuable source for small-area geographic studies. The Census Bureau has responded to public demand for more geographic coverage of census block data by expanding the Census Block Statistics Program each decade since block data first were published in 1940. ”

“ Indentations, Enclaves, and Exclaves Indentations occur where a low-density census block or cluster of blocks protrudes into the main body of the UA. Indentations almost always consist of territory outside of any place (only very rarely are they small incorporated places or CDPs) . Indentations formed by the boundaries of incorporated places usually occur more frequently than those involving only territory outside of any place. The inclusion of indentations smooths the UA boundary, gives it a more regular appearance, and simplifies its presentation on maps. ”

“ Defining MAs The MA standards specify the step-by-step definition process by which the concept of a densely settled core area plus its suburbs becomes realized as individual MSAs, CMSAs, PMSAs, and NECMAs. Qualification of an MSA requires the presence of a city of 50,000 or more inhabitants, or a Census Bureau-defined UA (of at least 50,000 inhabitants) and a total population of at least 100,000 (75,000 in New England) . The county or counties including the largest city in the core area of population become central counties of the MSA ”

“ Rural Places and Territory Territory, population, and housing units that the Census Bureau does not classify as urban are classified as rural. For instance, a rural place is any incorporated place or CDP with fewer than 2,500 inhabitants that is located outside of a UA. A place is either entirely urban or entirely rural, except for those designated as an extended city.
Extended Cities An extended city is an incorporated place that contains large expanses of sparsely populated territory for which the Census Bureau provides separate urban and rural population counts and land area figures. ”

“ In areas influenced by French settlement, such as within the State of Louisiana, the census block pattern preserves the riparian pattern of elongated strips of land, each having access to a major water feature. Rural areas in the central part of the country usually continue the grid-type road pattern of the urban core areas, primarily because of the introduction of the township and range survey system, but also due to the general lack of topographic relief. ”

“ Green often found it convenient to identify one individual in each city as a point of contact. He called these individuals key persons. The committees themselves became known as census tract committees. These were the forerunners of the present-day census statistical areas committees (see Chapter 3, “Local Census Statistical Areas Committees and Other Local Assistance”) . For the 1940 census, the Census Bureau adopted the census tract as an official geographic entity to be included in data tables of the standard publications of the decennial census. ”

“ Nonresidential urban land use Any type of cultural land use, such as parks, transportation facilities (airports and railyards) , factories, and office and industrial parks, that generally are not populated, but are considered to be integral parts of the urban landscape. When calculating the population density of a census block or AU to define a UA or extended city, the Census Bureau disregards the land area occupied by such land uses; the resultant population density figure more accurately reflects the residential density of the census block or AU. See also population density. ”

“ Undevelopable Territory As with jumps and nonresidential urban land uses, undevelopable territory also is used in some cases to link an outlying cluster of densely settled territory to the main body of the UA. The Census Bureau designates territory as undevelopable only if it consists of water area, mud flats, swamps, marshlands, steep slopes, and other terrain where development is nonexistent and new development is virtually impossible because of the physical limitations; such territory must not contain any existing housing or commercial structures. ”

“ The term consolidation is used when different levels of government are represented by a single entity; this new type of government has jurisdiction over the entire county or MCD area, unless some preexisting places are specifically excluded, as is the case with Lawrence, Beech Grove, Speedway, and Southport, Indiana, which have no governmental association with Indianapolis, Indiana. The Census Bureau defines a consolidated city as one wherein an additional incorporated place or places continue (s) to exist. ”

“ Physical size also can be an important factor in data analysis. To meet the latter need, the Census Bureau provides area measurements along with many of its 1990 census data tabulations.
The geographic coverage of each type of statistical area varies according to their purpose. To be of use, major regions and subregions usually must cover the entire Nation; that is, they must provide complete geographic coverage. By contrast, places and UAs, whose purpose is to distinguish more densely settled areas from the rest of the country, do not attain complete national geographic coverage. ”

“ Boundary Review The delineation of boundaries for American Indian and Alaska Native areas poses unique challenges for the Census Bureau. This is particularly true of legally or governmentally defined entities such as reservations and trust lands, the most important geographic units for the tabulation and presentation of decennial census data for the American Indian populations. The Census Bureau obtains boundaries for Federally recognized reservations and trust lands from the BIA, which certifies the accuracy of the boundaries depicted for these entities. ”