From a USGS Fact Sheet:
As one of the cornerstones of the U.S. Geological Survey’s (USGS) National Geospatial Program, The National Map is a collaborative effort among the USGS and other Federal, State, and local partners to improve and deliver topographic information for the Nation.
The National Map is featuring direct links to new and improved GIS data access utilities on a refreshed data delivery homepage at https://www.usgs.gov/NationalMap/data.
The following is a list of some of the capabilities available through the National Map applications.
•Create and export maps using The National Map’s online data. Even import your own data into the viewer for display and map creation.
• Search or browse The National Map’s extensive data catalog and select from several methods for downloading.
• Find and explore lidar point clouds in 3D through the Lidar Explorer.
•Access current and historical topo maps available in GeoPDF and GeoTIFF formats.
Direct to Complete Fact Sheet
2 pages; PDF.