Small Areas Census Data

Contents: Census Tracts / Block Numbering Areas (BNAs) | Block Groups | Blocks | ZIP Codes / ZCTAs | Glossary

Census Tracts / Block Numbering Areas (BNAs)

Definition
History
Maps and Reports: 2000 | 1990 | 1980–1940

Definition

Census Tracts are statistical subdivisions of counties. Tracts average 4,000 inhabitants, ranging from 2,500 to 8,000 inhabitants. Every Metropolitan Area or Urbanized Area in the United States is completely divided into tracts. Since the primary concern in defining tracts is the population, the land area of tracts varies widely. The boundaries are established by local committees, following guidelines set by the Census Bureau. Boundaries are intended to be stable from one census to another, to allow for meaningful comparisons. However, changes are made to tract boundaries if the population dramatically increases or decreases.

Tract numbers are unique only within the metropolitan or urban area. Tracts are assigned numbers from 0001 through 9499. Because tract areas are small and tract boundaries are drawn to reflect similarities in economic and housing characteristics, tracts are the statistical unit most often used to reflect neighborhoods.

Block Numbering Areas (BNAs) are statistically the equivalent of tracts, but they are outside of Metropolitan or Urban areas and the boundaries are defined by the Census Bureau. BNA numbers are unique only within the county. BNAs are assigned numbers from 9501 through 9989. For Census 2000 the entire country was "tracted" and the use of BNAs was discontinued.

History

Prior to 1990, much of the United States was not defined as either tracts or BNAs. State and local governments had the option of paying a fee to have their BNAs treated as tracts. For 1990, six states arranged to have complete tract coverage: Delaware, New Jersey, Connecticut, Rhode Island, California, and Hawaii. For Census 2000, all states have complete tract coverage.

The idea of collecting data by these small areas came from Dr. Walter Laidlaw, who was studying neighborhoods in New York City in 1906. For the 1910 Census, the Census Bureau, in response to his requests, made tabulations by census tracts for 8 cities which had a population of over 500,000; New York, Baltimore, Boston, Cleveland, Chicago, Philadelphia, Pittsburgh, and St. Louis. For 1920, the same eight cities were tabulated by tract. The number of cities was increased to 18 for 1930. The Census Bureau did not publish the data, but did make it available for purchase. Beginning with the 1940 Census, the Census Bureau established Census tract as an official geographic entity and included the tabulations for larger cities in its publications. (from "Statistics for Census Tracts" in 1950 Census of Population, vol. 1, p. 1. and Geographic Areas Reference Manual (GARM), chapter 10, pp. 1-3). Delaware areas were first tracted in 1960.

Census 2000

To use tract data, first identify the tract number. Census 2000 data and tract numbers can be located by street address. Otherwise, numbers must be determined by consulting tract maps.

American FactFinder. LOCATION: Internet (http://factfinder.census.gov/)

If you have a street address, use the street address search.

Use the Reference map feature by selecting "Maps and Geography" from the left menu, then Reference Maps. Select a state from the map and then zoom in small enough that tract boundaries are visible. If needed, recenter the map by typing in a ZIP code. Determine the correct tract number.

Then switch to Search (on the top menu bar), select the Geography tab, then "Show more selection methods and more geographic types", then change the search boxes to 2000 census, census tract, and the appropriate state, county, and tract number.

For Delaware tracts, use this shortcut to the Advanced geography search. Select the county, then tract number.

1990 Census

To use tract / BNA data, first identify the tract / BNA number. Beginning with the 1990 Census, data and tract numbers can be located by street address. Otherwise, numbers must be determined by consulting tract maps.

American FactFinder. LOCATION: Internet (http://factfinder.census.gov/)

To use the Reference Map feature: select "Data sets" from the left menu, scroll down to 1990, then select either the 100% data or the sample data, then the option Reference Maps. Select a state from the map and then zoom in small enough that tract boundaries are visible. If needed, recenter the map by typing in a street address or a ZIP code. Determine the correct tract number.

Then switch to Search (on the top menu bar), select the Geography tab, then "Show more selection methods and more geographic types", then change the search boxes to 1990 census, census tract, and the appropriate state, county, and tract number.

For Delaware tracts, use this shortcut to the Advanced geography search. Select the county, then tract number.

TIGER / Census Tract Street Index, 1990. Version 4. Washington, DC: U.S. Dept. of Commerce, Bureau of the Census, Data User Services Division, 2000. LOCATION: Morris Library - Microforms (DVD-ROM 1324)

CensusCD + Maps, 1990. East Brunswick, NJ: GeoLytics, 2000. LOCATION: Morris Library - Microforms (CD-ROM 1202): Contains 1990 and 1980 data and maps.

Census Geography for Delaware. Dover, DE: Delaware Development Office, State Data Center. LOCATION: Morris Library - Reference (Ref HA296 .N56) Reference Desk Census Shelf: Contains maps and narrative descriptions of the census tracts for 1980, with updates for 1990.

1990 Census Tract Maps of New Castle County, Delaware. University of Delaware Library. LOCATION: Internet (http://www2.lib.udel.edu/subj/maps/internet/delcens.htm)

Population and Housing Characteristics for Census Tracts and Block Numbering Areas, Maps. (CPH 3) Washington, DC: Department of Commerce, Bureau of the Census, 1992. LOCATION: Morris Library - U.S. Documents (U.S. Doc C 3.223/11:) Census Area: Local areas: Delaware (outside metropolitan areas) is number 9; Wilmington, DE--NJ--MD PMSA is number 259.

Digital Mapping Station. LOCATION: Morris Library - Lower Level: Data and maps for the entire country.

Tract Maps: 1990 Census. LOCATION: Morris Library - Reference (Ref microfiche 1993 2551-10): Tract maps available on ASI microfiche 1993 2551-10.

Census Tract / Block Numbering Area Outline Maps (Recreated), 1990. Washington, DC: Department of Commerce, Bureau of the Census, 2003. LOCATION: Morris Library - Microforms (DVD-ROM 1530): ADOBE PDF format. These maps are re-creations of the 1990 Census Tract / BNA outline maps and differ from the original 1990 Census Tract Outline Maps. Similar to the 2000 Census Tract outline maps, these maps are county-based and created for all 1990 Counties / County Equivalents in the United States. All maps display the 1990 geography; however, the features displayed on these maps are those shown on the Census 2000 maps. These maps show the boundaries and numbers of the 1990 census tracts / BNAs as well as the named features underlying the boundaries.

Summary Tape File 1A CD-ROM. (STF 1A) Washington, DC: Department of Commerce, Bureau of the Census. LOCATION: Morris Library - Microforms (various CD-ROM numbers): Tract data taken from the "short form" (100% count). Check DELCAT for CD-ROM call numbers.

1990 Population and Housing Characteristics: Census Tracts and Block Numbering Areas. (CPH-3) Washington, DC: Department of Commerce, Bureau of the Census, 1992. LOCATION: Morris Library - Reference (Ref CPH-3) Ref Desk Census Shelf (Local areas only) LOCATION: Morris Library - U.S. Documents (U.S. Doc C 3.223/11:) Census Area alphabetic section under "Population and Housing": Tract data taken from the "long form" (sample data).

Summary Tape File 3A CD-ROM. (STF 3A) Washington, DC: Department of Commerce, Bureau of the Census. LOCATION: Morris Library - Microforms (various CD-ROM numbers): Tract data taken from the "long form" (sample data). Delaware is covered on CD-ROM 147. Check DELCAT for other CD-ROM call numbers.

Census Tract Maps and Reports 1980–1940

CensusCD 1980. East Brunswick, NJ: GeoLytics, 2000. LOCATION: Morris Library - Microforms (CD-ROM 1201): Contains1980 data and maps.

1980 Census Geography for Delaware. Dover, DE: Delaware Development Office, State Data Center, 1982. LOCATION: Morris Library - Reference (Ref HA296 .N56) Census Shelf LOCATION: Morris Library - State Documents (HA296 .N56 1982) LOCATION: Morris Library - Map Collection (HA296 .N56 1982): Contains maps and narrative descriptions of the census tracts for 1980.

1980 U.S. Census Population & Housing Characteristics. San Diego, CA: National Decision Systems, 1982. LOCATION: Morris Library - Reference (Ref HA201 1980r ) vols 1-5: Delaware data is in volume 3, pages 204-209.

1980 Census of Population and Housing: Census Tracts. (PHC 80-2) Washington, DC: Department of Commerce, Bureau of the Census, 1983. LOCATION: Morris Library - U.S. Documents (U.S. Doc C 3.223/11: 980/nos.) Census Area alphabetic section under " Population and Housing": Maps are in pockets in back of reports. Wilmington, Delaware (including all of New Castle County) is report # 374; remainder of Delaware is report # 9.

1970 Census of Population and Housing: Census Tracts. (PHC 1) Washington, DC: Department of Commerce, Bureau of the Census, 1972. LOCATION: Morris Library - U.S. Documents (U.S. Doc C 3.223/11: 970/nos.) Census Area alphabetic section under " Population and Housing": Maps are in pockets in back of the reports. Wilmington, Delaware (including all of New Castle County) is report # 234.

1960 Census of Population and Housing: Census Tracts. Washington, DC: Department of Commerce, Bureau of the Census. LOCATION: Morris Library - U.S. Documents (U.S. Doc C 3.223/11: 960/nos.) Census Area alphabetic section under " Population and Housing": Maps are in pockets in back of reports. Wilmington, Delaware (including all of New Castle County) is report #173.

1950 Census of Population: Census Tracts. Washington, DC: Department of Commerce, Bureau of the Census. LOCATION: Morris Library - U.S. Documents (U.S. Doc C 3.950/nos.) Census Area alphabetic section under "Population": Maps are in back of reports. There are no tracted areas for Delaware.

Sixteenth Census of the United States, 1940. Washington, DC: Department of Commerce, Bureau of the Census. LOCATION: Morris Library - U.S. Documents Census Area (chronological section)

Population, Vol. 1: Number of Inhabitants
Population figures and maps are in the state reports, table 8. A list of cities which have tracts are listed in the United States summary report, p. 65. There are no tracted areas for Delaware.
Population and Housing: Statistics for Census Tracts
A series of 58 bulletins covering tracted cities. These bulletins were not incorporated into the final volumes. Not available at the University of Delaware Library.

Guide to Census Tract Resources. LOCATION: Internet (http://www.census.gov/geo/www/tractez.html)

Geographic Areas Reference Manual (GARM). U.S. Dept. of Commerce, Economics and Statistics Administration, Bureau of the Census, 1994. LOCATION: Morris Library - U.S. Documents (U.S. Doc C 3.6/2:G 29/4) Census Area LOCATION: Internet (http://www.census.gov/geo/www/garm.html)

Block Groups

A Block Group is a subdivision of a census tract or a block numbering area. A block group consists of all the blocks within a census tract beginning with the same number. Block group is the smallest geographic unit for which the Census Bureau tabulates sample data. Block group is the smallest census geography available for 1990 in American Factfinder and in 1990 Census Look-up.

2000 | 1990 | 1980–1940

Census 2000

American FactFinder. LOCATION: Internet (http://factfinder.census.gov/)

Use the Reference map feature by selecting "Maps and Geography" from the left menu, then Reference Maps. Select a state from the map and then zoom in small enough that block group boundaries are visible. If needed, recenter the map by typing in a ZIP code. Determine the correct tract number, and block group number.

Then switch to Search (on the top menu bar), select the Geography tab, then "Show more selection methods and more geographic types", then change the search boxes to 2000 census, block, and the appropriate state, county, and tract number, and block group number.

For Delaware block groups, use this shortcut to the Advanced geography search. Select the county, then tract number, etc.

1990

American FactFinder. LOCATION: Internet (http://factfinder.census.gov/)

Use the Reference map feature by selecting "Maps and Geography" from the left menu, then Reference Maps. Select a state from the map and then zoom in small enough that block boundaries are visible. If needed, recenter the map by typing in a ZIP code. Determine the correct tract number, block group number, and block number.

For Delaware block groups, use this shortcut to the Advanced geography search. Select the county, then tract number, etc.

1980–1940

See the sources for Block data.

Blocks

Definition
2000
Maps: 1990–1980
Reports: 1990–1980
Maps and Reports: 1970–1940

Definition

Blocks are the smallest area of Census geography. Blocks are bounded primarily by streets or other visible features but may also be bounded by governmental unit boundaries. Many blocks correspond to individual city blocks but blocks – especially in rural areas – may include many square miles. Blocks do not cross the boundaries of counties, tracts, or Block Numbering Areas (BNAs). In 1940, the Census Bureau began publishing census block data for all cities with 50,000 or more inhabitants, including Wilmington, Delaware. 1990 was the first time the Census Bureau established blocks covering the entire nation. Only 100% data are available at the Block level. Note: to find blocks, you must first find the census tract number. Block data from the 1990 Census are not available in American FactFinder or Census Lookup.

Census 2000

American FactFinder. LOCATION: Internet (http://factfinder.census.gov/)

For Delaware blocks, use this shortcut to the Advanced geography search. Select the county, then tract number, etc.

1990-1980 Maps

Kent County, Delaware, 1990. LOCATION: Morris Library - Map Collection (G3833 .K4 E25)

New Castle County, Delaware, 1990. LOCATION: Morris Library - Map Collection (G3833 .N4 E25)

Sussex County, Delaware, 1990. LOCATION: Morris Library - Map Collection (G3833 .S8 E25)

Digital Mapping Station. LOCATION: Morris Library - Lower Level: Data and maps for the entire country.

1980 Block Statistics Maps. (PHC 80-1) Washington, DC: Department of Commerce, Bureau of the Census. LOCATION: Morris Library - U.S. Documents Microfiche (U.S. Doc Microfiche C3.224/5:) LOCATION: Morris Library - U.S. Documents (U.S. Doc C 3.224/5:) Census Area alphabetic section under "Population and Housing" Selected areas only: Series consists of 374 maps issued in microfiche format. Wilmington, Delaware (including all of New Castle county) is report # 374; remainder of Delaware is report # 9.

1990–1980 Reports

Census of Population and Housing (1990): Block Statistics: Summary Tape File 1B. (STF 1B) Washington, DC: Department of Commerce, Bureau of the Census, 1992. LOCATION: Morris Library - Microforms (CD-ROM 130) Local areas only LOCATION: Morris Library - Microforms (various CD-ROM numbers): Check DELCAT for call numbers for areas outside the local area.

1980 Census of Population and Housing, Block Statistics Reports. (PHC 80-1) Washington, DC: Department of Commerce, Bureau of the Census. LOCATION: Morris Library - U.S. Documents Microfiche (U.S. Doc Microfiche C3.224/5:980 nos.) LOCATION: Morris Library - U.S. Documents (U.S. Doc C 3.224/5:) Census Area alphabetic section under "Population and Housing" (Local areas only): Series consists of 374 reports issued in microfiche format. Wilmington, Delaware (including all of New Castle county) is report # 374; remainder of Delaware is report # 9.

Maps and Reports: 1970–1940

1970 Census of Housing, Block Statistics. LOCATION: Morris Library - U.S. Documents (C3. 224/5:970 nos.) Census Area alphabetic section under "Housing": Maps are either in back of report or in folder next to report. Wilmington, Delaware (including all of New Castle county) is report # 43.

1960 Census of Housing, vol. 3: City Blocks. LOCATION: Morris Library - U.S. Documents (C3. 224/5:960 nos.) Census Area alphabetic section under "Housing": Maps are in back of reports. These reports cover characteristics of housing units. Wilmington, Delaware (including all of New Castle county) is report # 104.

1950 Census of Housing, vol. V, Block Statistics. Washington, DC: Department of Commerce, Bureau of the Census, 1951-2. LOCATION: Morris Library - U.S. Documents (C 3.950-8:5/nos.) Census Area alphabetic section under "Housing": Maps in back of reports. These reports cover characteristics of housing units. Wilmington, Delaware (including all of New Castle County) is report # 208.

Sixteenth Census of the United States, 1940. Washington, DC: Department of Commerce, Bureau of the Census. LOCATION: Morris Library - U.S. Documents Census Area (chronological section)

Housing, Vol. I: Supplement...Block Statistics for Cities
A series of 195 bulletins, including one for Wilmington, Delaware. These bulletins were not included in the final report. Not available at the University of Delaware Library.
Housing. Analytical Maps...Block Statistics
A series of 96 folio sized maps of cities, including one for Wilmington, Delaware.

Definition

ZIP stands for Zone Improvement Plan. A ZIP Code identifies a specific geographic delivery area as identified by the U.S. Postal Service (USPS). Because they are created for mail delivery, the area of a ZIP Code may change to suit USPS operations. ZIP Code® is a registered trademark of the U.S. Postal Service. The 1990 decennial Census was the first time the Census Bureau widely released data at the ZIP code level.

For Census 2000, the Census Bureau decided not to release any data by ZIP Code and created a new geographic entity called ZIP Code Tabulation Area (ZCTA). ZCTAs are generalized area representations of U.S. Postal Service (USPS) ZIP Code service areas. ZCTA^TM is a trademark of the U.S. Census Bureau.

2000 Reports and Maps

American FactFinder. LOCATION: Internet (http://factfinder.census.gov/): AFF has 2000 data and maps by ZCTA. Use the Advanced Geography Search. Summary Files 1–4 contain data by ZCTA.

1990 Reports

Summary Tape File 3B: ZIP Code Areas (1990). (STF 3B) Washington, DC: Department of Commerce, Bureau of the Census, 1993. LOCATION: Morris Library - Microforms (CD-ROM 199)

Sourcebook of ZIP Code Demographics. Fairfax, VA: CACI, Inc. LOCATION: Morris Library (HA203 .S66)

1990 Maps

The U.S. Government does not issue maps of ZIP codes.

Sourcebook of 5 Digit ZIP Code Maps. Fairfax, VA: CACI, Inc., 1987. LOCATION: Morris Library - (G3692 .P8 S68 1987)

New Castle County, Delaware, Street Map Book. Alexandria, VA: ADC, 2002. LOCATION: Morris Library - Reference (Ref G1268 .N4 A33 2002) At Reference Desk LOCATION: Morris Library - Map Collection (Folio+ G1268 .N4 A33)

Kent County, Delaware, Street Map Book. Alexandria, VA: ADC, 1999. LOCATION: Morris Library - Reference (Ref G1268 .K4 A4 1999) At Reference Desk LOCATION: Morris Library - Map Collection (Folio+ G1268 .K4 A4)

ZIP Code Statistics. LOCATION: Internet (http://www.census.gov/epcd/www/zipstats.html): Census Bureau guide to data by ZIP codes. Includes information on 1997 and 1992 Economic Censuses and ZIP Business Patterns.

ZIP Code® Tabulation Areas (ZCTAs^TM). LOCATION: Internet (http://www.census.gov/geo/ZCTA/zcta.html): Gives definitions and products. For Census 2000, there are no ZIP Code products of any kind available from the Census Bureau; the nearest equivalent is the data available by ZCTA.