Census Tract
A small, relatively stable geographic subdivision of a county designed by the Census Bureau to contain approximately 4,000 people for demographic data collection.
Census tracts are the most commonly used geographic unit for neighborhood-level demographic analysis. The Census Bureau designs tracts to be relatively homogeneous with respect to population characteristics, economic status, and living conditions. Each tract has a numeric code up to 6 digits (with an implied decimal), prefixed by the state and county FIPS codes to form a unique 11-digit GEOID.
There are approximately 85,000 Census tracts in the United States. Tracts are revised after each decennial Census: those exceeding 8,000 residents are typically split, while those falling below 1,200 may be merged.
Although Census tracts and ZIP codes serve different purposes, they are frequently linked in data analysis. A single ZIP code may overlap multiple tracts, and crosswalk files mapping ZIPs to tracts (provided by HUD and others) are essential tools for researchers who need to bridge postal and Census geographies.