DLG maps are vector representations of planimetric and topographic map features. These features may be derived from cartographic source materials or from aerial photographs. DLG maps use manual and automated digitizing methods and on doing so, contain a wide variety of information from vegetation cover, to administrative boundaries, to roads, basic topography, and more. The DLG file below shows the transportation available for sale and the transportation in progress in the state of Illinois.
http://pubs.usgs.gov/of/2003/of03-471/domier/index.html
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