https://www.census.gov/geo/maps-data/data/tiger.html
The TIGER/LineShapefiles are extracts containing selected geographic and cartographicinformation from the Census Bureau’s MAF/TIGER® (Master Address File /Topologically Integrated Geographic Encoding and Referencing) database. TheMAF/TIGER database was developed at the Census Bureau to support a variety ofgeographic programs and operations including functions such as mapping,geocoding, and geographic reference files that are used in decennial andeconomic censuses and sample survey programs. Spatial data for geographicfeatures such as roads, railroads, rivers, and lakes, as well as legal andstatistical geographic areas are included in the product. Other informationabout these features, such as the name, the type of feature, address ranges,and the geographic relationship to other features, also are included. TheTIGER/Line Shapefiles are made available to the public for no charge and aretypically used to provide the digital map base for a Geographic InformationSystem or for mapping software.
The 2008 TIGER/Line Shapefiles contain current geographic areas (boundaries of governmental units as of January 1, 2008), Census 2000 vintage geography, and Economic Census geography. The shapefiles also contain some additional feature updates reported in the Boundary and Annexation Survey (BAS). All counties have now been realigned as a result of the MAF/TIGER Accuracy Improvement Project (MTAIP) and are included in the 2008 TIGER/Line Shapefiles. For more information about the MTAIP please refer to the 2008 TIGER/Line Shapefile Technical Documentation available in [pdf] or Text.