Census Block Group Distance Database
Census Block Groups are from Census 2000 SF1 and Census 2010 SF1 files. Census Block Groups (BGs) are "statistical divisions of census tracts, are generally defined to contain between 600 and 3,000 people, and are used to present data and control block numbering....A BG usually covers a contiguous area."
The size of the file increases with the radius. Smaller files (<=.5 or <= 1 or <= 5 miles) may be easier to use if only distances <=.5 or <= 1 or <= 5 miles respectively are needed.
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