Geographic Terms and Concepts -
Codes for Geographic Entities

The Census Bureau and other federal agencies assign codes to geographic entities to facilitate the organization, presentation, and exchange of statistical data and other information.  Geographic entity codes allow for the unambiguous identification of individual entities, generally within a specific, higher-level geographic entity (for example, county codes are assigned uniquely within each state).  For geographic entities that have names (such as states, counties, places, county subdivisions, urban areas, and metropolitan and micropolitan statistical areas), codes generally are assigned alphabetically based on name.

Census Bureau data products contain several types of geographic entity codes: Federal Information Processing Series (FIPS), American National Standards Institute (ANSI), and Census Bureau codes.

Federal Information Processing Series (FIPS)—These are codes formerly known as Federal Information Processing Standards codes, until the National Institute of Standards and Technology (NIST) announced its decision in 2005 to remove geographic entity codes from its oversight.  The Census Bureau continues to maintain and issue codes for geographic entities covered under FIPS oversight, albeit with a revised meaning for the FIPS acronym.  Geographic entities covered under FIPS include states, counties, congressional districts, core based statistical areas, places, county subdivisions, subminor civil divisions, consolidated cities, and all types of American Indian, Alaska Native, and Native Hawaiian areas.  FIPS codes are assigned alphabetically according to the name of the geographic entity and may change to maintain alphabetic sort when new entities are created or names change.  FIPS codes for specific geographic entity types are usually unique within the next highest level of geographic entity with which a nesting relationship exists.  For example, FIPS state, congressional district, and core based statistical area codes are unique within nation; FIPS county, place, county subdivision, and subminor civil division codes are unique within state.  The codes for American Indian, Alaska Native, and Native Hawaiian areas also are unique within state; those areas in multiple states will have different codes for each state.

American National Standards Institute (ANSI)—With the removal of geographic entities from Federal Information Processing Standards oversight, the Census Bureau and other federal agencies have sought American National Standards Institute (ANSI) oversight authority for geographic entity codes.  These codes are referred to as "National Standard" codes in some Census Bureau products.  Geographic entities covered under ANSI include states, counties, congressional districts, core based statistical areas and related statistical areas, places, county subdivisions, consolidated cities, subminor civil divisions, and all types of American Indian, Alaska Native, and Native Hawaiian areas—Alaska Native regional corporations, Alaska Native village statistical areas, American Indian reservation and off-reservation trust lands, American Indian tribal subdivisions, Hawaiian home lands, Oklahoma tribal statistical areas, state designated tribal statistical areas, and tribal designated statistical areas.

Relationship between FIPS and ANSI codes—Geographic entities for which NIST formerly provided Federal Information Processing Standards oversight will continue to be referred to as FIPS (Federal Information Processing Series) codes in some Census Bureau data products, despite the Census Bureau having sought ANSI oversight authority.  These geographic entities include states, counties, congressional districts, and core based statistical areas and related statistical areas.  The Census Bureau continues to maintain and issue codes for these entities following the same structure and without change to existing codes, except when necessary to maintain alphabetic sorting based on names of entities.  The Census Bureau also continues to maintain and issue five-digit FIPS codes (formerly FIPS 55) for places, county subdivisions, consolidated cities, subminor civil divisions, Alaska Native Regional Corporations, and all types of American Indian, Alaska Native, and Native Hawaiian areas but is not seeking ANSI oversight authority for these entity codes.  The U.S. Geological Survey has ANSI oversight authority for its Geographic Names Information System identifier (GNIS ID), which has been adopted as a National Standard (NS) code for states, counties, places, county subdivisions, subminor civil divisions, consolidated cities, Alaska Native Regional Corporations, and all types of American Indian, Alaska Native, and Native Hawaiian areas.  The Census Bureau will include the GNIS ID for these entities in its data products, portrayed as an eight-digit character numeric code and identified as "ANSI." NS codes (GNIS IDs) will not sort geographic entities in alphabetical order based on name or title, as is the case with FIPS codes.

Census Bureau codes—The Census Bureau assigns and issues codes for a number of geographic entities for which FIPS or ANSI codes are not available, and sometimes in addition to FIPS and ANSI codes.  Geographic entities for which census codes are assigned and issued in Census Bureau data products include regions, divisions, census tracts, block groups, census blocks, urban areas, and all types of American Indian, Alaska Native, and Native Hawaiian areas.  Some codes—voting district, state legislative district, and school district—use standards established by the states—or for school districts, the U.S. Department of Education.

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