Reference files are the what, why, and how of Census geography.  What are the definitions of geographic terms, why are geographic areas defined, and how do we define geographic areas.  Find reference information such as FIPS and ANSI codes, geographic boundary change notes, significant county boundary changes, and county adjacency information.

Residence Datasets 1 and 2 on the Census 2000 Special EEO Tabulation provide data only for counties of 50,000 or more. Counties of less than 50,000 were merged with other counties into County Sets. These are the guidelines used to create and name these county sets.