2020 Census Block Groups for King County

For more information about this layer please see the GIS Data Catalog. 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如需了解该图层的更多信息，请参阅GIS数据目录（GIS Data Catalog）。本图层为每个街区组（block group）提供了地理标识符（geographic identifier）GEO_ID_GRP，该标识符是人口普查与调查数据的关键字段，涉及的调查与普查包括十年一次人口普查（Decennial Census）、经济普查（Economic Census）、美国社区调查（American Community Survey）以及人口估计计划（Population Estimates Program）。美国人口普查局（Census Bureau）的多项普查与调查数据均可通过该局的公开数据发布网站（https://data.census.gov/）获取。所有包含人口统计数据的原始TIGER/Line形状文件（TIGER/Line shapefiles）与地理数据库，TIGER/Line形状文件是从美国人口普查局的主地址文件（Master Address File, MAF）/拓扑集成地理编码与参照数据库（Topologically Integrated Geographic Encoding and Referencing Database, MTDB）中提取的精选地理与制图信息。该形状文件涵盖全美50个州、哥伦比亚特区（District of Columbia）、波多黎各（Puerto Rico）以及各岛屿地区（美属萨摩亚（American Samoa）、北马里亚纳群岛联邦（Commonwealth of the Northern Mariana Islands）、关岛（Guam）、美属维尔京群岛（United States Virgin Islands））的相关信息。此类形状文件包含地理区域与要素的多边形边界、包括道路与水文要素在内的线性特征，以及点状特征。此类形状文件不包含受《美国法典》（United States Code, U.S.C.）第13编保护的敏感数据或机密数据。标准街区组是同一普查分区（census tract）内的街区集群，其4位普查街区编号的首位数字相同。例如，普查分区1210.02内的街区3001、3002、3003至3999均属于街区组3。由于十年间发生的边界与要素变更，当前的街区组未必始终保持上述街区编号与街区组的对应关系。例如，因普查分区边界调整，街区3001可能会发生归属变动。2020年人口普查划定的街区组通常涵盖600至3000名居民，且一般为连片区域。每个普查分区包含一个或多个街区组，且街区组在所属普查分区内拥有唯一编号。在标准普查地理层级体系中，街区组不会跨越县或普查分区的边界，但可能会跨越县分区、地方行政区域、城市区域、选举区、国会选区以及美国印第安人、阿拉斯加原住民与夏威夷原住民区域（AIANNH areas）的边界。街区组的有效编号范围为0至9。以0开头的街区组通常对应沿海、五大湖水域及领海区域。美国人口普查局并未将普查分区边界延伸至五大湖或3海里领海极限处，而是沿海岸线或近海划定了部分普查分区的边界。完整技术文档：https://www2.census.gov/geo/pdfs/maps-data/data/tiger/tgrshp2020/TGRSHP2020_TechDoc.pdf