U.S. Census Bureau U.S. Census Bureau Block Relationship Files [html] http://www.census.gov/geo/maps-data/data/relationship.html Geographic relationship files Relationship Files 2010 to 2000 Census Block and Tract Relationship Files http://www.census.gov/geo/maps-data/data/relationship.html [html] ZCTA Relationship Files "relationship files" Census Tract Relationship File: 2000 to 2010 2010 to 2000 Census Block and Tract Relationship Files Block Relationship Files 2010 to 2000 Census Block and Tract Relationship Files 2010 Census Tract Relationship Files U.S. Census Bureau U.S. Census Bureau