Cartographic Products Management Branch
20000101
2000 Census Block Groups
vector digital data
http://www.census.gov/geo/www/cob/bg2000.html
A census block group (BG) is a cluster of census blocks having the
same first digit of their four-digit identifying numbers within a
census tract. (See also Census Tract.) For example, block group 3
(BG 3) within a census tract includes all blocks numbered from 3000
to 3999. BGs generally contain between 600 and 3,000 people, with an
optimum size of 1,500 people. Most BGs were delineated by local
participants as part of the U.S. Census Bureau's Participant
Statistical Areas Program. The U.S. Census Bureau delineated BGs only
where a local, state, or tribal government declined to participate or
where the U.S. Census Bureau could not identify a potential local or
tribal participant. BGs never cross the boundaries of states, counties,
or statistically equivalent entities, except for a BG delineated by
American Indian tribal authorities, and then only when tabulated within
the American Indian hierarchy. (See also Tribal Block Group.) BGs never
cross the boundaries of census tracts, but may cross the boundary of any
other geographic entity required as a census block boundary.
In decennial census data tabulations, a BG may be split for statistical
purposes for every unique combination of American Indian area, Alaska
Native area, Hawaiian home land, congressional district, county
subdivision, place, voting district, or other tabulation entity. For
example, if BG 3 is partly in a city and partly outside the city, there
are separate tabulated records for each portion of BG 3. BGs are used in
tabulating data nationwide, as was done for the 1990 census, for all
block-numbered areas in the 1980 census, and for selected areas in the
1970 census. For statistical purposes, BGs are a substitute for the
enumeration districts (EDs) used for reporting data in many parts of the
United States for the 1970 and 1980 censuses and in all areas before 1970.
The cartographic boundary files are a generalized extract from the
U.S. Census Bureau's TIGER database. Line simplification/smoothing
was performed with a tolerance of 0.005 decimal degrees and a
coordinate reduction using the Douglas-Peucker method with a
tolerance of 0.0003 decimal degrees. Very small polygons were
eliminated when the combination of geographic codes existed
elsewhere. The geography was clipped back to the shoreline of the
United States, in contrast to TIGER/LineŽ which shows the full
extent of geography out to the 3-mile limit.
These generalized cartographic boundary files are originally
produced to support the spatial geographic infrastructure
for certain mapping functions within the Census Bureau's
American Fact Finder and in support of the LandView
Geographic Data Viewer. The generalized files have a much
smaller file size than the original file extraction from the
Census Bureau's TIGER database, resulting in faster download
and processing times.
20000101
publication date
As needed
172.46087000
-65.22152710
71.34294128
17.88511467
ISO 19115 Topic Categories
boundaries
None
Cartographic
Boundary
generalized
government
boundaries
statistical
Block Group
census block
census block group
FGDC Framework Themes
FWGOVERNMENTALUNITS
None
United
States
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
DC
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Puerto Rico
None
The boundaries in this file are for statistical purposes only. They do not represent legal boundaries.
U.S. Census Bureau, Geography Division,
Geographic Products Management Branch
mailing
4700 Silver Hill Road, Stop 7400
Washington
DC
20233-7400
US
physical
8903 Presidential Parkway, Room 520 WP1
Upper Marlboro
Maryland
20772
US
301-763-1128
301-457-4710
tiger@census.gov
7am - 5pm EST
http://www.census.gov/geo/www/maps/CP_Contact.htm
20030514
U.S. Census Bureau, Geography Division,
Cartographic Products Management Branch
Cartographic Products Management Branch Metadata
Coordinator
mailing
4700 Silver Hill Road, Stop 7400
Washington
DC
20233-7400
US
physical
8903 Presidential Parkway, Room 301 WP1
Upper Marlboro
Maryland
20772
US
301-763-1101
301-457-4710
zachariah.meade.turner.iii@census.gov
7am - 5pm EST
http://www.census.gov/geo/www/maps/CP_Contact.htm
FGDC Content Standards for Digital Geospatial
Metadata
FGDC-STD-001-1998