Using census data successfully requires close attention to geographic definitions. Researchers must do more than merely locate a number. They must also associate the number to the correct geography. Otherwise the data becomes invalid. Selected geographies that are used most often are defined below.

• United States.
• Regions : Four regions cover the Northeast, Midwest, South, and West.
• Divisions : The four regions are subdivided into the following nine divisions: New England; Middle Atlantic; East North Central; West North Central; South Atlantic; East South Central; West South Central; Mountain; and Pacific.

  Click here for a map and a list of states in census regions and divisions.

• States.
• Metropolitan statistical areas (MSAs): MSAs usually include central cities of 50,000 or more population, plus the surrounding suburbs that are socially and economically integrated with the central city. For example, the Buffalo Metropolitan Statistical Area includes the City of Buffalo (central city), plus all remaining parts of Erie and Niagara Counties. It is very important to differentiate Buffalo City from Buffalo MSA. Statistics for each are very different.
• Counties.
• County subdivisions (Minor Civil Divisions--MCDs): Primary divisions of counties, such as cities and towns. New York State considers villages places, not county subdivisions.
• Places (or parts): Places in New York State are cities and villages. They are sometimes divided among multiple county subdivisions. For example, the Village of Williamsville is in both Amherst and Cheektowaga Towns.

The following table provides examples of differences between county subdivisions and places using the City of Buffalo, the Village of Williamsville, and the Town of Amherst as examples.

	Place	County Subdivision (Minor Civil Division)
City of Buffalo	X	X
Village of Williamsville	X
Town of Amherst		X

• Census tracts: Subdivisions of counties that have approximately 4,000 people. Cite tracts in relation to particular counties because all counties will have tract 1,…
• Block groups: Subdivisions of census tracts that include groups of adjacent blocks.
• Census blocks: Bounded on all sides by boundaries.

Figure 1 below illustrates relationships among census tracts, block groups, and census blocks. Tract 1 includes 20 census blocks, 1001 through 5004, and five block groups. The initial digit of a block determines the block group number. For example, block group 1 includes blocks 1001-1004. Blocks and block groups must be cited in relation to a census tract because any number of tracts will have block 1001 and block group 1. Data for block groups are at the identical level of detail as tracts. However, the Bureau of the Census publishes very limited statistics for individual blocks due to confidentiality restrictions.

Figure 1
Census Tract 1

Block Group 1	Block Group 2	Block Group 3	Block Group 4	Block Group 5
Block 1001	Block 2001	Block 3001	Block 4001	Block 5001
Block 1002	Block 2002	Block 3002	Block 4002	Block 5002
Block 1003	Block 2003	Block 3003	Block 4003	Block 5003
Block 1004	Block 2004	Block 3004	Block 4004	Block 5004

Retrieving statistics for census tracts, block groups, and blocks requires use of maps so that the data can be associated with particular areas.

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Locating Census Maps

2000 Block Maps (US. Census Bureau)
http://ftp2.census.gov/geo/maps/blk2000/
Reproduces block maps for the entire nation in PDF format.

2000 Tract Maps (US. Census Bureau))
http://ftp2.census.gov/plmap/pl_trt/
Reproduces tract maps for the entire nation in PDF format.

Census Atlas of the United States (US. Census Bureau)
http://www.census.gov/population/www/cen2000/censusatlas/
Reproduces approximately 800 maps most of which cover the 2000 census. Nearly 150 maps pertain to historical data. Topics deal with population distribution; race and hispanic origin; age; sex; living arrangements; place of birth, citizenship, and ancestry; migration; language; education; income and poverty; and housing. Information includes text and charts, as well as maps.

Erie and Niagara Counties, New York : An Index to Census 2000 Block Maps compiled by Giann A. Palachuvattil, student, School of Library and Information Studies, University at Buffalo. http://library.buffalo.edu/libraries/units/lml/govdocsubj/census2000/Erie_Niag.Tract_Index_2000.pdf Lockwood Reference G3803.E6E25 2000 .P34
An index to the 2000 Erie and Niagara County block maps. Organization is by tract numbers and by names of places and MCDs.

Erie and Niagara County Block Maps (2000 Census of Population and Housing) (US. Census Bureau)
Located in Lockwood Library Reference Department outside the Reference Office.
Lockwood Library's Reference Department has large printed reference copies of block maps for Erie and Niagara Counties used with the 2000 Census.

National Historical Geographic Information System (NHGIS) (University of Minnesota. Population Center)
http://www.nhgis.org/
Download state and county boundary files covering 1790-2000, and census tract boundary files covering 1940-2000 for use with GIS software. Intended users are those experienced with or seriously learning GIS packages. People who need an occasional map, but are uninterested in learning GIS systems, should use Social Explorer. NHGIS also offers statistical data for the censuses of 1790-2000.

Social Explorer (City University of New York. Queens College)
http://library.buffalo.edu/libraries/e-resources/socialexplorer.html
Provides maps and statistical reports for places, census tracts, block groups, counties, and congressional districts for 1940-2000. Specific geographies may vary for each census. Coverage also includes maps and data for religious affiliations by counties for 1980-2000. Social Explorer is intended for those who need an occasional map, but have no interest in learning a GIS system. More serious map users ought to consider National Historical Geographic Information System (NHGIS) as an alternative. A guide, Social Explorer-Creating Census Maps and Statistical Tables is at http://library.buffalo.edu/libraries/asl/guides/busdoc/census/social_explorer.pdf.

US Census Bureau Geography (US. Census Bureau)
http://www.census.gov/geo/www/
Emphasis is upon products relating to the 2000 Census. Topics cover block maps; TIGER files used with geographic information systems; the revised definition of urban area; and geographic definitions.

US Census Bureau Maps and Cartographic Resources (US Bureau of the Census)
http://www.census.gov/geo/www/maps
Links connect to geographic products suitable for both novice and more advanced data users. Options cover new developments; "Map Products" covers outline maps in PDF format, and "Boundary Files" includes data for use with GIS packages. Other choices lead to online mapping sites and related Web pages.

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