The National Map is the U.S. Geological Survey's program for delivering foundational geospatial base data for the United States. Through its download client you can pull standardized national layers: the 3D Elevation Program (3DEP) DEMs and lidar point clouds, the National Hydrography Dataset, transportation, governmental boundaries, structures, land cover, and orthoimagery.
Because everything is produced to consistent national specifications and released into the public domain, The National Map is the go-to source when you need authoritative, license-free base layers for the U.S. — whether you are building terrain analysis, watershed models, or a cartographic basemap in Atlas.