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Census Geography

Through its many surveys, the Census Bureau reports data for a wide variety of geographic types, ranging from the entire United States down to a Census Block. The geographic types that a survey reports on will depend upon the survey's purpose, and how the data were collected.

diagram of census geographic relationships


The diagram shows the many geographic types for which data are available in FactFinder. In general, larger geographic types (e.g., state) are shown near the top and smaller geographic types (e.g., census tract) are shown towards the bottom.

With connecting lines, the diagram also shows the hierarchical relationships between geographic types. For example, a line extends from states to counties because a state is comprised of many counties, and a single county can never cross a state boundary. To uniquely name a county, the state name must be included (e.g., Orange County, California; Orange County, Florida).

If no line joins 2 geographic types, then an absolute and predictable relationship does not exist between them. For example, many places are confined to one county. However, some places extend over more than one county, such as New York City. Therefore, an absolute hierarchical relationship does not exist between counties and places, and any tabulation involving both these geographic types may represent only a part of one county or one place.

Notice that many lines radiate from blocks, indicating that most geographic types can be described as a collection of blocks, the smallest geographic unit for which the Census Bureau reports data. However, only two of these lines also describe the path by which a block is uniquely named. That is, the path through the Block Group or through the Tribal Block Group.


Note: To read definitions of the geographic types, click Glossary on the banner of American FactFinder.