The BAS annexation data comprise of attribute information for legal boundary changes, which local, county, and state governments reported to the Boundary and Annexation Survey (BAS) and the BAS State Certification Program. Legal boundary changes are changes to incorporated place boundaries resulting from a legal action such as an annexation or deannexation/detachment. The annexation data do not include boundary corrections that were not implemented by a legal action.
DISCLAIMER: The U.S. Census Bureau makes no claims to the completeness of the annexation data in the boundary change files. The data in these files were collected through the BAS and BAS State Certification program in which local, county, and state governments voluntarily participated. The level of completeness and accuracy of the data are subject to the participants’ continued effort in providing the Census Bureau with up to date boundary information. In addition, the BAS Year does not necessarily correspond to the year in which the boundary change went into effect. By policy, the Census Bureau will accept legal boundary changes from BAS participants as long as these changes were in effect as of January 1 of the active BAS Year. For example, during the 2010 BAS, the Census Bureau accepted legal boundary changes from previous years up to January 1, 2010. When researching boundary changes effective from a particular year, be sure to search multiple BAS Year ranges since governments may report effective boundary changes during a later BAS Year. Also, be advised that information collected prior to the 2011 BAS is archival; several boundary change records in these files may no longer be in effect or may be superseded by later boundary change actions. The Census Bureau deemed the boundary changes to be in effect during the time of collection and during tabulation for the decennial census. Please read the file descriptions below before downloading the data files.
|BAS Year(s)||Effective Date||Census||Available Format(s)||File Description|
|2012||January 1, 2012||Excel, TXT||TXT|
|2011||January 1, 2011||Excel, TXT||TXT|
|2001-2010||January 1, 2010||2010||Excel, TXT||TXT|
|1991-2000||January 1, 2000||2000||Excel, TXT||TXT|
|1981-1990||January 1, 1990||1990||TXT|
|1971-1980||January 1, 1980||1980||TXT|
Note: Boundary change files prior to the 2011 BAS contain archival data used for the corresponding decennial census. These data will not be updated in these files. Be advised that several records in the archives may no longer be valid or may be modified by a later boundary change action.