GIS Data Catalog

Summary

2020 United States Census Bureau block group census geography.

Converted from Census Bureau TIGER/Line shapefiles and updated to meet King County GIS standards.

Major water bodies - Puget Sound, Lake Washington, Lake Sammamaish, and Lake Union have been removed.

Description

This layer contains a geographic identifier (GEO_ID_GRP) for each block group that is the key field for the data from censuses and surveys such as Decennial Census, Economic Census, American Community Survey, and the Population Estimates Program.

Data from many of the Census Bureau’s surveys and censuses, are available at the Census Bureau’s public data dissemination website ( https://data.census.gov/ ).

All original TIGER/Line shapefiles and geodatabases with demographic data are available atThe TIGER/Line Shapefiles are extracts of selected geographic and cartographic information from the Census Bureau's Master Address File (MAF)/Topologically Integrated Geographic Encoding and Referencing (TIGER) Database (MTDB).

The shapefiles include information for the fifty states, the District of Columbia, Puerto Rico, and the Island areas (American Samoa, the Commonwealth of the Northern Mariana Islands, Guam, and the United States Virgin Islands).

The shapefiles include polygon boundaries of geographic areas and features, linear features including roads and hydrography, and point features.

These shapefiles do not contain any sensitive data or confidential data protected by Title 13 of the U.S.C.Standard block groups are clusters of blocks within the same census tract that have the same first digit of their 4-character census block number (e.g., Blocks 3001, 3002, 3003 to 3999 in census tract 1210.02 belong to block group 3).

Current block groups do not always maintain these same block number to block group relationships due to boundary and feature changes that occur throughout the decade.

For example, block 3001 might move due to a change in the census tract boundary.

Block groups delineated for the 2020 Census generally contain 600 to 3,000 people and a block group usually covers a contiguous area.

Each census tract contains one or more block groups and block groups have unique numbers within census tract.

Within the standard census geographic hierarchy, block groups never cross county or census tract boundaries, but may cross the boundaries of county subdivisions, places, urban areas, voting districts, congressional districts, and AIANNH areas.Block groups have a valid range of zero (0) through nine (9).

Block groups beginning with a zero generally are in coastal and Great Lakes water and territorial seas.

Rather than extending a census tract boundary into the Great Lakes or out to the 3-mile territorial sea limit, the Census Bureau delineated some census tract boundaries along the shoreline or just offshore.

Full documentation: https://www2.census.gov/geo/pdfs/maps-data/data/tiger/tgrshp2020/TGRSHP2020_TechDoc.pdf