DLG

http://web.wt.net/daba/dlg/default.html

A DLG, or Digital Line Graph, is a cartographic feature that is represented in digital vector form. DLG's contain a wide variety of information, including topography, hydrography, boundaries, roads, and contours. All of this information is compiled by the USGS and distributed for use in GIS applications and more. The DLG displayed above is of a portion of Yellowstone National Park, and includes roads, contours, lakes, streams, and section lines.