2021 Block Groups ACS

Block Groups (BGs) are clusters of blocks within the same census tract. Each census tract contains at least one BG, and BGs are uniquely numbered within census tracts. BGs have a valid code range of 0 through 9. BGs have the same first digit of their 4-digit census block number from the same decennial census. BGs coded 0 are intended to only include water area, no land area, and they are generally in territorial seas, coastal water, and Great Lakes water areas. Block groups generally contain between 600 and 3,000 people. A BG usually covers a contiguous area but never crosses county or census tract boundaries. They may, however, cross the boundaries of other geographic entities like county subdivisions, places, urban areas, voting districts, congressional districts, and American Indian / Alaska Native / Native Hawaiian areas. The American Community Survey (ACS) is an ongoing, annual survey conducted by the U.S. Census Bureau that provides detailed, up-to-date data on the social, economic, housing, and demographic characteristics of the U.S. population. Launched in 2005 to replace the decennial census long form, it samples approximately 3.5 million households annually to assist in federal funding allocation and community planning. For more information, contact: GIS Manager, Research & Strategic Projects (RSP) Montgomery County Planning Department, MNCPPC T: 301-650-5620街区组（Block Groups，BGs）是隶属于同一普查区的街区集群。每个普查区至少包含一个街区组，且街区组在其所属普查区内具有唯一编号。街区组的有效代码取值范围为0至9。来自同一次十年人口普查的街区组，其4位普查街区编号的首位数字均相同。代码为0的街区组仅包含水域，无陆地区域，通常分布在领海、近岸海域以及五大湖水域范围内。街区组的人口规模通常介于600至3000人之间。街区组通常覆盖连片区域，且绝不会跨越县或普查区的行政边界，但可跨越其他地理实体的边界，例如县分区、聚居地、城市区域、选举区、国会选区以及美洲印第安人/阿拉斯加原住民/夏威夷原住民聚居区。美国社区调查（American Community Survey，ACS）是由美国人口普查局开展的持续性年度调查，可为美国人口提供社会、经济、住房以及人口特征方面的详细最新数据。该调查于2005年启动，用以替代十年一次人口普查的长表问卷，每年约抽样350万户家庭，用于辅助联邦资金分配与社区规划工作。如需了解更多信息，请联系：蒙哥马利县规划部研究与战略项目（Research & Strategic Projects，RSP）地理信息系统经理，MNCPPC，联系电话：301-650-5620