This line shapefile represents the county boundary lines of the United States at 1:100,000 scale.This layer is part of the 2014 ESRI Data and Maps collection for ArcGIS 10.2. U.S. County Boundaries provides detailed boundary lines consistent with the county, block group, tract, and state data sets and are effective for cartographic display at regional and state levels. TomTom North America and ESRI. (2014). United States County Boundaries, 2010-2011. ESRI. Available at: http://purl.stanford.edu/xx132wq1375