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 Geocodes are basic components of the TIGER data base and the geographic reference files that the Census Bureau develops and maintains to process the results of its censuses and sample surveys. Together with the TIGER data base, these files form the basis for the tabulation and dissemination of the collected data in their proper geographic entity. Geocodes obviate the need to relate data to geographic entities by name only; instead, the Census Bureau’s processing operations associate data with the geocodes that are surrogates for the names of geographic entities.

In addition to the Census Bureau’s MCD/CCD code (discussed later in this section), there are other geocodes that are part of the Federal Information Processing Standards (FIPS) system, developed by the National Institute of Standards and Technology (NIST) and now maintained by the U.S. Geological Survey. (The Census Bureau’s MCD/CCD code scheme is not part of the FIPS code scheme.) The FIPS 55 system identifies named entities in the United States, Puerto Rico, the Virgin Islands of the United States, and the Pacific Outlying Areas. The scheme features a two-digit numeric State code and a five-digit numeric locality code that uniquely identify each named entity. The system further distinguishes between types of named entities by means of a two-character class code, consisting of a leading alphabetic character and a number. There are 11 different class codes applicable to county subdivisions; in combination with the State code and locality code, they provide additional information about each county subdivision.

The FIPS 55 locality codes identify governmentally functioning MCDs within a numeric range from 00001 to 89999. The codes in this range also represent incorporated places, CDPs, and Alaska Native and American Indian areas, together with other entities not included in the tabulations of the decennial census, such as named localities, military installations, and National Parks. All these entity names are combined and listed in a single alphabetic sequence. The FIPS code range, 90000 to 98999, is reserved for CCDs and nonfunctioning MCDs where they cover whole States, whole counties, or their statistically equivalent entities. The FIPS 55 locality codes together with the FIPS 55 class codes provide a unique identifier for the 8-28County Subdivisions