Census Block Boundaries 2020

From the 2022 TIGER/Line Technical Documentation: Census blocks are statistical areas bounded on all sides by visible features (e.g., streets, roads, streams, and railroad tracks), and by non-visible boundaries (e.g., city, town, township, county limits, and short line-of-sight extensions of streets and roads). Generally, census blocks are small in area (e.g., a block in a city). Census blocks in suburban and rural areas may be large, irregular, and bounded by a variety of features (e.g., roads, streams, and/or transmission line rights-of-way). In remote areas, census blocks may encompass hundreds of square miles. Census blocks cover all territory in the United States, Puerto Rico, and the Island Areas. Blocks do not cross the boundaries of any entity for which the Census Bureau tabulates data. (See Figures 12 and 13). Census Block Numbers—Census blocks are numbered uniquely within the boundaries of each state, county, census tract with a 4-character census block number. The first character of the tabulation block number identifies the block group. A block number can only be unique by using the decennial census state (STATEFP<yr>), county (COUNTYFP<yr>), census tract (TRACTCE<yr>), and block (BLOCKCE<yr>)+. There is no consistency in block numbers from census to census.摘自2022年TIGER/Line技术文档：普查区块（Census blocks）是一类统计区域，其边界由各类可见地物（如街道、道路、溪流与铁轨）及不可见边界（如城市、城镇、镇区、县界，以及街道和道路的短视距延伸段）共同界定。通常而言，城市中的普查区块面积较小。郊区与农村地区的普查区块面积可能较大、形状不规则，边界由多种地物界定，例如道路、溪流和/或输电线路通行权用地。在偏远地区，单个普查区块的覆盖范围可达数百平方英里。普查区块覆盖美国、波多黎各及各岛屿地区的全部领土。普查区块不会跨越美国人口普查局（Census Bureau）进行数据统计的任何行政实体的边界。（详见图12与图13）。普查区块编号——在每个州、县、普查区的边界范围内，普查区块均采用4位字符的编号以实现唯一标识。普查区块统计编号的首位字符用于标识其所属的区块组（block group）。仅通过十年一次人口普查对应的州代码（STATEFP<yr>）、县代码（COUNTYFP<yr>）、普查区代码（TRACTCE<yr>）及区块代码（BLOCKCE<yr>）等组合，才能确保区块编号的唯一性。不同十年一次人口普查的区块编号体系并不统一。