Types of Census Geographic Area

Census geographic entities are organized by the U.S. Bureau of the Census into hierarchies for tabulating and reporting statistics.  These entities include a range or geography from census blocks (the smallest and most numerous type of geographic entity) to an entity for the entire United States.  Each step up in the hierarchy has fewer units.

States are combined to form regions and divisions, and are subdivided into counties and/or statistically equivalent entities.  Counties in Michigan are further subdivided into Minor Civil Divisions(MCD's)which include cities and townships and Places which include cities and villages. 

Counties are also divided into census tracts which are further divided into block groups (BG's) and blocks. Census blocks are the smallest type of geographic entity identified by the Census Bureau.  Census block numbers are assigned within each census tract and all blocks sharing the same first digit in their identifying numbers make up a block group.  These geographies are considered Small-Area Geographies.

Regions and Divisions - The United States is divided into four regions: Northeast, South, Midwest, and the West.  The regions are then divided into nine divisions, with each region having two or more divisions.  Michigan belongs to the Midwest Region and the East North Central division.

Counties - Primary legal and administrative subdivisions of states.

Minor Civil Divisions (MCD's) - Legally defined county subdivisions.  Cities and Townships in Michigan.


Incorporated Places - Entities incorporated under the laws of each State.  In Michigan, places are treated as parts of townships.


Congressional Districts (CD's) - 435 Congressional Districts throughout the United States.  Michigan has 15 Congressional Districts from which representative are elected to the U.S. House of Representatives.


Voting Districts - Voting districts including election districts, precincts, legislative districts and wards as defined by state and local governments for the purpose of conducting elections.


ZIP Codes - ZIP Code geographic entities are established by the U.S. Postal Service to expedite mail delivery.  They do not have specific linear boundaries and frequently cross state, county, and city boundaries.


Metropolitan Areas (new definitions)- These areas are designated and defined by the Federal Office of Management and Budget (OMB) following a set of published standards.


The December 27, 2000 Federal Register includes a notice announcing OMB's adoption of Standards for Defining Metropolitan and Metropolitan Statistical Areas. These new standards replace and supersede the 1990 standards for defining metropolitan areas. The new standards reflect decisions reached by OMB on standards recommended by the interagency Metropolitan Area Standards Review Committee and in response to public comment on those recommendations. OMB will apply the new standards with Census 2000 data and will announce definitions based on these standards in 2003.


The adoption of these new standards will not affect the availability of Federal data for geographic areas such as states, counties, county subdivisions, and municipalities. For the near term, the Census Bureau will tabulate and publish data from Census 2000 for all metropolitan areas in existence at the time of the census (that is, those areas defined as of April 1, 2000).


Urban and Rural - The U.S. Census Bureau classifies as urban all territory, population, and housing units located within urbanized areas (UAs) and urban clusters (UCs). It delineates UA and UC boundaries to encompass densely settled territory, which generally consists of:


- A cluster of one or more block groups or census blocks each of which has a population density of at least 1,000 people per square mile at the time, and


- Surrounding block groups and census blocks each of which has a population density of at least 500 people per square mile at the time, and


- Less densely settled blocks that form enclaves or indentations, or are used to connect noncontiguous areas with qualifying densities.


Rural consists of all territory, population, and housing units located outside of UAs and UCs. Geographic entities, such as metropolitan areas, counties, minor civil divisions (MCDs), and

places, often contain both urban and rural territory, population, and housing units.


Urban Cluster (UC) - An urban cluster (UC) consists of densely settled territory that has at least 2,500 people but fewer than 50,000 people. (A UC can have 50,000 or more people if fewer than 35,000 people

live in an area that is not part of a military reservation.)

The U.S. Census Bureau introduced the UC for Census 2000 to provide a more consistent and accurate measure of the population concentration in and around places. UCs replace the provision

in the 1990 and previous censuses that defined as urban only those places with 2,500 or more people located outside of urbanized areas.


Urban Cluster Central Place - A central place functions as the dominant center of a UC. The U.S. Census Bureau identifies one or more central places for a UC, with a preference for the most

populous incorporated place(s). (Some UCs do not have a central place.) Urban Cluster Title and Code. The title of a UC may contain up to three incorporated place names, and will include the two-letter U.S. Postal Service abbreviation for each state into which the UC extends. However, if the UC does not contain an incorporated place, the UC title will include the single name of the geographic entity that occurs first from the following list: census designated place (CDP), minor civil division (MCD), or populated place recognized by the U.S. Geological Survey.


Urbanized Area (UA)- An urbanized area (UA) consists of densely settled territory that contains 50,000 or more people. The U.S. Census Bureau delineates UAs to provide a better separation of urban and rural territory, population, and housing in the vicinity of large places. At least 35,000 people in a UA must live in an area that is not part of a military reservation.

For Census 2000, the UA criteria specify that the delineations be performed using a zero-based approach. Because of the more stringent density requirements and the less restrictive extended

place criteria, some territory that was classified as urbanized for the 1990 census has been reclassified as rural. (Area that was part of a 1990 UA has not been automatically grand fathered into the 2000 UA.) In addition, some areas that were identified as UAs for the 1990 census have been reclassified as urban clusters.


Census Designated Places (CDP's) - These entities are designed to recognize significant population concentrations that are not located in incorporated places, but have characteristics similar to such places, including community identity, high population density, and commercial development