Geographic Reference Files are documents that list codes for geographic entities. These include Relationship Files, Gazetteer Files, Block Assignment Files, and Tally Files.
Relationship Files describe geographic relationships over time and between types. Geographic Relationships Over Time show the relationships (comparability) for the same type of geography over different periods of time (e.g. the relationship between places in 2010 and 2000). Geographic Relationships Between Entity Types show the relationship between different types of geography for the same period (e.g. the relationships between congressional districts and places).
Gazetteer Files list geographic entities, such as county, place, and census tracts, with information on name, geographic code, population, housing unit counts, and latitude/longitude of the internal point.
Block Assignment Files (BAFs) are among the geographic products that the Census Bureau provides to states and other data users containing the small area census data necessary for legislative redistricting.
Tally Files provide the total number of geographic entities for a given area. For example, the 2010 Census National Geographic Tallies list 11,078,297 census blocks and 3,143 counties and equivalents.