The Boundary and Annexation Survey (BAS) annexation data are composed of attribute information for legal boundary changes, which state, county, and local governments reported to the BAS and the BAS State Certification Program. Legal boundary changes are changes to county, incorporated place, and minor civil division 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.

Legal Boundary Change Files for Active Incorporated Places

BAS Year(s)	Effective Date	Census	Available Format(s)	File Description
2023	January 1, 2023		Excel, TXT	TXT
2022	January 1, 2022		Excel, TXT	TXT
2021	January 1, 2021		Excel, TXT	TXT
2020	January 1, 2020		Excel, TXT	TXT
2019	January 1, 2019		Excel, TXT	TXT
2018	January 1, 2018		Excel, TXT	TXT
2017	January 1, 2017		Excel, TXT	TXT
2016	January 1, 2016		Excel, TXT	TXT
2015	January 1, 2015		Excel, TXT	TXT
2014	January 1, 2014		Excel, TXT	TXT
2013	January 1, 2013		Excel, TXT	TXT
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	PDF	TXT
1971-1980	January 1, 1980	1980	PDF	TXT

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 state, county, and local 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 in the table above 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 before downloading the data files.