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Boundary and Access Survey (BAS)

What is the BAS?

The Census Bureau conducts the BAS each year to provide tribal, state, and local governments the opportunity to submit changes to legal boundaries, names, and governmental status effective on or before January 1 of the survey year. However, a subset of the 40,000 legal governments nationwide forms the core ‘reporting universe’ for BAS production each year. The reporting universe for the 2017 BAS consists of all governments with a 2,500 or greater population count. The BAS is voluntary and every legal government has the opportunity to participate each year.

The Census Bureau works closely with the U.S. Bureau of Indian Affairs to ensure that the BAS reflects official boundaries for federally recognized American Indian reservations, off-reservation trust lands, and tribal subdivisions.

When Does the BAS Occur?

In December each year, all governmental units are given an opportunity to participate in the next year’s BAS. The Census Bureau has conducted the BAS annually since 1971 (with cancellations in 1993 and 2014). The majority of boundary-related processing activities occur from January through August.

Why Do We Conduct the BAS?

The Census Bureau conducts the annual BAS to assure current and accurate boundaries of governmental units for use in tabulating and presenting statistical data released from censuses and surveys such as the annual American Community Survey. The BAS fulfills the agency’s responsibility as part of the National Spatial Data Infrastructure, for which the Office of Management and Budget (OMB) Circular A-16 designates the Census Bureau as the lead federal agency for maintaining national data about governmental units and statistical and administrative boundaries. These boundaries are important in providing governments current information about their communities for future planning.

Who Uses the BAS Results?

The Census Bureau provides the results of the BAS to the public as part of the agency’s annual TIGER/Line product and via the TIGERweb online mapping application. The public and data users rely on the annual BAS boundaries as the official federal representation of boundaries for legal governmental units. 

The Census Bureau uses the BAS results to support a number of programs, including Congressional and State Legislative redistricting, the Decennial Census and related preparatory tests, the Economic Census, and the Special Census Program. The ACS uses BAS boundaries to tabulate survey results, and the Population Estimates Program uses BAS to ensure that the most current boundaries are available in the annual release of population estimates. 

Numerous federal programs rely on accurate boundaries from each BAS.  The U.S. Geological Survey depicts the annual BAS boundaries on the National Map online.  The Department of Housing and Urban Development uses BAS boundaries to determine jurisdictional eligibility for various grant programs, such as the Community Development Block Grant program.  The Department of Agriculture uses BAS boundaries to determine eligibility for various rural housing and economic development programs.


TIGERweb & TIGERweb applications allow visualization of TIGER (Topologically Integrated Geographic Encoding and Referencing database) data.

BAS Flyer (Boundary and Annexation Survey)
Tribal BAS Flyer



‚ÄčAn accurate population count starts with an up-to-date and complete address list. The LUCA program provides state, local and tribal governments with a once-in-a-decade opportunity to update the Census Bureau’s address list that is used to conduct the decennial census. State, local and tribal government participation in the 2020 LUCA program can contribute to a more accurate population count for their communities. The page will be updated as new information becomes available.

Visit the LUCA website for more information

LUCA Informational Workshops

LUCA workshops were held in mid-2017 in northern and southern Nevada to provide an overview of the program, explain how it will benefit your community, and provide an opportunity to ask questions. The workshops also covered program goals, participation methods, and security guidelines.

2020 Luca Promotional Presentation
2020 Luca Promotional Script