DRG

"Digital Raster Graphic (DRG) images of USGS standard series quadrangles cover systematically subdivided areas of latitude with formats ranging from 7.5- by 7.5-minutes to 1- by 2-degrees. DRG's of standard quadrangles range in scale from 1:20,000 to 1:250,000. DRG's coverages include the conterminous United States, Alaska, Hawaii, Puerto Rico and the Virgin Islands"--DRGP̲KG.TXT file.