Boundary and Annexation Survey (BAS)

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Guidance for Geography Users

BAS Reference Maps

Maps that display the updated legal boundaries and names valid through January 1, 2018, for all governmental units that participated in the 2018 BAS.

File Naming Conventions

Information about how Boundary and Annexation Survey map files are named.

BAS Code Lists

All federally recognized American Indian areas, counties, incorporated places, consolidated cities, and governmental MCDs are identified by a unique BAS ID.

Last Revised: December 4, 2017

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