Zip Code Database Definitions of Geographic Concepts, including Maps

United States ZIP Code Directory

States

States are the primary governmental divisions of the United States. The District of Columbia is treated as a statistical equivalent of a State for census purposes.

(Statistics for Puerto Rico, the U.S. Virgin Islands, Guam, and the Northern Mariana Islands are published only in the separate 1997 Economic Censuses of Outlying Areas, and are not included in any United States totals.)

Each State and equivalent is assigned a two-digit numeric Federal Information Processing Standards (FIPS) code (ST) in alphabetical order by State name (e.g., Alabama=01, Wyoming=56). In files for Mining, additional codes appear in the state field for offshore areas (codes 80-83). In files for Construction, codes 91 to 94 are used in the state code field to identify census regions.

Counties

Counties and their equivalents, 3,141 in all, are the primary political and administrative divisions of States. These areas are called parishes in Louisiana. In Alaska, 23 boroughs and "census areas" are treated as county equivalents for census purposes. Several cities (Baltimore, MD, St. Louis, MO, Carson City, NV, and 41 cities in Virginia) are independent of any county organization and, because they constitute primary divisions of their States, are accorded the same treatment as counties in census tabulations. That part of Yellowstone National Park in Montana is treated as a county equivalent. The District of Columbia has no primary divisions, and the entire area is considered equivalent to a county for statistical purposes. Kalawao County, HI, is combined with Maui County for statistical purposes.

Counties are identified by a 3-digit Federal Information Processing Standards (FIPS) code, which is sequenced alphabetically within state, except for the independent cities, which follow the listing of counties within state.

Places

Incorporated Places -- The 1997 Economic Census provides information for legally defined, incorporated municipalities (cities, towns, villages, and boroughs) with 2,500 or more inhabitants as of the 1990 population census. Hawaii does not have incorporated places that are recognized for census purposes, so data there are provided for census designated places (CDP's) with 2,500 or more inhabitants. All told, data are presented for 6920 places in the United States.

Selected Towns and Townships -- Some county subdivisions, such as towns and townships, are not classified as incorporated places for census purposes. Statistics are presented in the 1997 Economic Census for towns in the six New England states, New York, and Wisconsin, and townships in Michigan, Minnesota, New Jersey and Pennsylvania with a 1990 census population of 10,000 or more. These 669 towns and townships are presented in the same tables as places.

The place code is a five-digit FIPS code assigned to places (including independent cities) in alphabetic sequence within a state. Its use largely replaces that of the 4-digit census place code used in 1987 and earlier censuses.

All incorporated municipalities with populations of fewer than 2,500, town and townships not qualifying as noted above, and the remainders of counties outside places are categorized as "Balance of county" and assigned a place code of "99999".

Consolidated City - A consolidated city is a unit of local government for which the functions of an incorporated place and its county or minor civil division (MCD) have merged. The legal aspects of this action may result in both the primary incorporated place and the county or MCD continuing to exist as legal entities, even though the county or MCD performs few or no governmental functions and has few or no elected officials. Where this occurs, and where one or more other incorporated places in the county or MCD continue to function as separate governments, even though they have been included in the consolidated government, the primary incorporated place is referred to as a "consolidated city."

Consolidated cities appear only in selected files. They appear immediately after the appropriate county data and immediately before the records for the semi-independent places and "consolidated city (balance)" that comprise them.

Each consolidated city is assigned a one-character alphabetic census code. Each consolidated city also is assigned a five-digit FIPS code that is unique within State. The semi-independent places and the "consolidated city (remainder)" carry the same consolidated city code, but have their own five- digit FIPS place codes that are unique within State.

Metropolitan Areas (MSA's, CMSA's and CBSA's)

Metropolitan areas in general - The general concept of a metropolitan area (MA) is one of a large population nucleus, together with adjacent communities that have a high degree of economic and social integration with that nucleus. Some MA's are defined around two or more nuclei.

Each MA must contain either a place with a minimum population of 50,000 or a Census Bureau-defined urbanized area and a total MA population of at least 100,000 (75,000 in New England). An MA comprises one or more central counties. An MA also may include one or more outlying counties that have close economic and social relationships with the central county. An outlying county must have a specified level of commuting to the central counties and also must meet certain standards regarding metropolitan character, such as population density, urban population, and population growth. In New England, MA's are composed of cities and towns rather than whole counties.

The territory outside MA's is referred to as "nonmetropolitan."

MA's are defined under the auspices of the U.S. Office of Management and Budget.

Consolidated and Primary Metropolitan Statistical Areas (CMSA's and PMSA's) - If an area that qualifies as an MA has more than one million persons, primary metropolitan statistical areas (PMSA's) may be defined within it. PMSA's consist of a large urbanized county or cluster of counties that demonstrates very strong internal economic and social links, in addition to close ties to other portions of the larger area. When PMSA's are established, the larger area of which they are component parts is designated a consolidated metropolitan statistical area (CMSA).

In statistical tables, data for the MSA's and CMSA's are intermingled in alphabetic sequence, with the PMSA's presented alphabetically under their parent CMSA's.

Metropolitan Statistical Areas (MSA's) - Metropolitan statistical areas (MSA's) are relatively freestanding MA's and are not closely associated with other MA's. These areas typically are surrounded by nonmetropolitan counties. The MSA's have largely been replaced by the new governmental statistical areas called CBSA's.

Over half of all metropolitan areas changed boundaries between the 1987 and 1992 economic censuses, largely reflecting changes in commuting patterns as shown in the 1990 population census. There were no boundary changes implemented between the 1992 and 1997 censuses, although several new MSA's were added (Hattiesburg, MS MSA; Flagstaff, AZ-UT MSA; Grand Junction, CO MSA; Jonesboro, AR MSA; and Pocatello, ID MSA). The MSA's used in the 1997 Economic Census are those defined as of June 30, 1996. Missoula, MT MSA was created in 1998, so is not reflected in 1997 Economic Census data.

Each metropolitan area is assigned a four-digit FIPS code, in alphabetical order nationwide. If the fourth digit of the code is a "2," it identifies a CMSA. PMSA's are identified by the CMSA code together with a separate four-digit FIPS PMSA code.

MSA/CMSA and PMSA codes are carried on the records of the counties and places that comprise them, except for counties in New England where MA's may cross county boundaries. New England counties are assigned MSA and PMSA codes of "0000". Outside of New England, nonmetropolitan counties and places have MSA and PMSA codes of "9999".

Core-Based Statistical Areas (CBSA's)

New metropolitan and micropolitan statistical area definitions were announced by OMB on June 6, 2003, based on application of the 2000 standards with Census 2000 data. Metropolitan and Micropolitan Statistical Areas are collectively referred to as Core-Based Statistical Areas.

Metropolitan and micropolitan statistical areas are defined in terms of whole counties or county equivalents, including the six New England states. As of June 6, 2003, there were 362 metropolitan statistical areas (metro) and 560 micropolitan statistical areas (micro) in the United States. As of August 31, 2010, there are 370 "metro" areas and 584 "micro" areas.

Previous reports using Census 2000 data have employed metropolitan area boundaries defined by the Office of Management (OMB) as of June 30, 1999 and based on 1990 standards. Under the 1990 standards, each metropolitan area included a city of 50,000 or more population or a Census Bureau-defined urbanized area of at least 50,000 population, provided that the component county/counties had a population of at least 100,000. Metropolitan areas consisted of one or more counties, except in the New England States, where the components were cities and towns. Metropolitan areas included metropolitan statistical areas (MSAs) and consolidated metropolitan statistical areas (CMSAs). CMSAs were composed of primary metropolitan statistical areas (PMSAs). There were 258 MSAs, 73 PMSAs and 18 CMSAs in the United States.

Metropolitan statistical areas defined under the 2000 standards with Census 2000 data may not be directly comparable to MSAs and CMSAs defined as of 1999. In addition to the designation of new micropolitan statistical areas, the following kinds of changes may affect the definition of individual metropolitan areas in existence in 1999 and redefined based on Census 2000 data and the 2000 standards:

ZIP Codes

ZIP Codes are administrative entities of the U.S. Postal Service. Limited statistics are summarized for individual five-digit ZIP Codes in manufacturing, retail trade, and several of the service sectors. These statistics are generally limited to a count of the establishments in each industry or kind of business, further classified by size. In addition, statistics on employment, payrolls, and sales or receipts are presented for nonmanufacturing businesses by sector businesses within a ZIP Code, not by individual kind of business.

ZIP Codes generally do not coincide with the Census Bureau's geographic or political areas, and they change according to postal requirements. Most ZIP Codes do not have specific boundaries, and their implied boundaries do not necessarily follow clearly identifiable physical features. At the time of the 1997 Economic Censuses, there were about 40,000 ZIP Codes, although several thousand had no business activity and are not included in files.

Outlying Areas

The 1997 Economic Censuses of Outlying Areas provide data for--

The Census Bureau does not collect economic census data for American Samoa or the Trust Territory of the Pacific Islands.

Special-Purpose Areas

Offshore Areas

The census of mineral industries presents some statistics on petroleum and natural gas industries for selected offshore areas (as well as by State).

Regions

Census regions are groupings of States that subdivide the United States for the presentation of data. Data are summarized by region only for construction industries. There are four regions--Northeast, Midwest, South, and West. Each of the four census regions is divided into two or more census divisions. Prior to 1984, the Midwest region was named the North Central region.

Regions (nonstandard)The Current Industrial Report series presents selected statistics for other nonstandard regions--for example, "brick industry regions" and "lumber industry regions" in appropriate reports.

Major Retail Centers (MRC's) and Central Business Districts (CBD's). MRC's and CBD's were large concentrations of retail stores within metropolitan areas, reported in the census of retail trade from 1948 to 1982. This series of reports was discontinued because of the high cost of defining the areas. For some purposes, the statistics for ZIP Codes can substitute for the discontinued MRC and CBD statistics.

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