Census Geographies


Census geography is organized on several different levels. Some of the levels fit completely within one another, while others may cross the boundary of a larger level.

The basic hierarchical organization of census geography is Nation > States > Counties > County Subdivisions > Census Tracts > Block Groups > Blocks, with each level nested completely within its predecessor.

These levels cover all areas in the United States, and added up, the total population equals the entire population of the United States. Other levels, such as places, can cross the boundaries of other levels, and some, such as ZIP codes, do not cover all areas of the United States. ZIP codes only cover those areas where mail is delivered.


The diagram above shows the relationships between different levels of census geographies. A line between two levels represents a hierarchical relationship between them, meaning that the larger level, generally displayed near the top of the diagram, can be subdivided into a smaller level.

Here’s more information on basic census geographies:

You can also explore data by ZCTA (zip codes), School Districts (UNSD, SCSD, ELSD), Metropolitan Statistical Areas (MSA), Public Use Microdata Areas (PUMA), Congressional Districts, and many other geographic levels. Head over to this guide for information on these geographic levels.