Census Block Boundaries - SCAG Region

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. Blocks do not cross the boundaries of any entity for which the Census Bureau tabulates data. 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, county, census tract, and block. There is no consistency in block numbers from census to census.人口普查街区（Census blocks）是一类统计区域，其四周由可见地物（如街道、公路、溪流与铁轨）以及不可见边界（如城市、城镇、镇区、县界，以及街道和公路的短视距延伸段）划定范围。一般而言，城市内的人口普查街区面积较小。郊区与农村地区的人口普查街区则可能面积较大、形状不规则，且由多种地物（如道路、溪流以及/或输电线路通行权区域）划定边界。在偏远地区，单个人口普查街区的覆盖范围可达数百平方英里。人口普查街区不会跨越美国人口普查局（Census Bureau）负责统计数据的任何实体的边界。人口普查街区编号——在每个州、县、普查区（census tract）内，人口普查街区均采用4位字符的编号实现唯一标识。该编号的首位字符用于标识街区组（block group）。街区编号的唯一性需结合十年一次人口普查的州、县、普查区以及街区信息共同确定。不同次人口普查的街区编号体系并不具备一致性。