Office of Geographic Information
MassGIS has processed a portion of the U.S. Census Bureau's 2010 data release for Massachusetts for GIS users who may need access to demographic datasets. These are only suitable for use with Census 2010 products and should NOT be linked to geography or tables from the Census 2000 release. Available from MassGIS are the three levels of Census Boundary Areas, used by the Bureau to collect and tabulate decennial census data. These include Blocks - areas bounded on all sides by visible features, such as streets, roads, streams, and railroad tracks, and by non-visible boundaries such as city, town, township, and county limits, and short line-of-sight extensions of streets and roads; Block Groups - clusters of blocks within the same census tract that have the same first digit of their 4-digit census block number and Tracts - clusters of block groups which generally have a total population size between 1,200 and 8,000 people with an optimum size of 4,000 people. For more information on Census geography, see Geographic Shapefile Concepts Overview(Chapter 5 of the 2010 TIGER/Line Shapefiles Technical Documentation). For attribute definitions, see sections 5.2 (Blocks), 5.3 (Block Groups), and 5.4 (Tracts). The complete set of documentation is available at tttp://www.census.gov/geo/www/tiger/tgrshp2010/documentation.html.