Census block group

A census block group is a geographical unit used by the United States Census Bureau. Census block groups are one step above census blocks and one step below census tracts in the geographic hierarchy and generally contain between 600 and 3,000 people. Census block groups usually cover a contiguous area and never cross state, county, or census tract boundaries but may cross the boundaries of any other geographic entity. A block group consists of clusters of blocks within the same census tract that have the same first digit of their four-digit census block number. For example, 3001, 3002, and 3003 belong to block group 3 in their respective census tract.