2010. Stackhouse, Cecil and United States. Bureau of Transportation Statistics. This polygon shapefile depicts nonattainment and maintenance areas for the United States and its Territories for the enforcement of the sulfur diox... United States. Bureau of Transportation Statistics.
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2010. U.S. Census Bureau. Geography Division and Environmental Systems Research Institute (Redlands, Calif.). This polygon shapefile represents the 2010 Census urban areas in the United States. An urban area comprises a densely settled core of census tracts... Environmental Systems Research Institute (Redlands, Calif.).