From a USGS Announcement:
What’s “1”? It’s the new set of digital cartographic frameworks from The National Atlas of the United States of America. Prepared at one million-scale (where an inch on a map is nearly 16 miles) this authoritative and integrated national dataset has twice the detail of previous versions.
This is the first time the Federal government has ever released these basic digital map themes at 1:1,000,000-scale:
- Boundaries (national, state, and county)
- Transportation (roads, railroad, railroad stations, airports, and ports)
- Surface waters (coastlines, streams, gaging stations, waterbodies, and wetlands, all fully networked)
- Cities and towns
This new release serves as the foundation for small-scale maps and datasets on the Nation’s people, heritage, and resources. The new map data is delivered at no cost and is available on-line as a web map service from nationalatlas.gov
By moving to one million-scale, the National Atlas achieves two goals to better serve national and international audiences. First, map features have been harmonized at the U.S. borders of Canada and Mexico with data from national mapping programs in those nations for use in the Environmental Atlas of North America. Also, a second edition of the data that conforms to the specifications of the Global Map is ready. Global Map is an international effort by government mapping organizations to make a consistent map of the world at one million-scale
Future releases are scheduled to include: Federal and Native American lands, Congressional Districts, U.S. Statistical areas and more.
See Also: National Atlas Online Map Maker