The 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. The BAFs contain Census tabulation block codes and geographic area codes for a specific geographic entity type. These BAFs are designed to be used in conjunction with the Name Lookup Tables, if names are needed.
BAFs have been created for each of the 50 states, the District of Columbia, and the Commonwealth of Puerto Rico. Each file contains 2020 Census tabulation block codes and geographic area codes for a specific geographic entity type. Each BAF contains every block within the given state, even if the block is not within one of the geographic areas represented in the file. For those blocks where no geographic area is present, the block is listed, followed by one or more pipe delimiters (depending on the file layout for the specific geographic area type). BAFs are not created for a geography type when that geography type does not exist in the state.