Census Data Resources: Census Geography

• The boundaries of many census geographic units are based on population density.  Because of this, the boundaries change annually.
• The nation was not broken down into tracts, block groups, and blocks for all censuses. For example, there are many portions of North Carolina that were not broken down into tracts in 1980.
• The same geographies are used for both the decennial long form and the ACS.

The same geographies are used for both the decennial and the ACS.