This polygon shapefile contains the boundaries of the United States, Puerto Rico, and the U.S. Virgin Islands. The map layer was created by extracting county polygon features from the 2006 Census TIGER/Line files produced by the U.S. Census Bureau. These files were then merged into a single file and the county and State boundaries were dissolved, leaving the national boundary. This is a revised version of the July 2012 map layer. This layer is part of the 1997-2014 edition of the National Atlas of the United States.These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:1,000,000-scale data. No responsibility is assumed by the National Atlas of the United States in the use of these data.