This data represents the map extent for current and historical USGS topographic maps for the United States and Territories, including 1 X 2 Degree, 1 X 1 Degree, 30 X 60 Minute, 15 X 15 Minute, 7.5 X 7.5 Minute, and 3.75 X 3.75 Minute. The grid was generated using ESRI ArcInfo GIS software.
