Geosciences

• U. S. Geological Survey Maps
• U.S. Geological Survey Aerial Photography    
• USGS Landsat Project  (see also NASA’s Landsat link below)
• National Satellite Land Remote Sensing Data Archive
• ​National Elevation Dataset

NASA Visible Earth

​Earth Observatory (Natural Hazards, Global Maps)

Radar Imaging

· Airborne Synthetic Aperture Radar (AIRSAR) data

· Shuttle Radar Topography Mission (SRTM) data

Various sites provide access to historical and current U. S. Census data and maps. They include:

National Historical Geographic Information System (NHGIS): includes aggregate and statistical data and boundary files for years between 1790 and 2000.

Social Explorer: The free edition offers demographic maps from 1790-2007.

EPA – for maps and spatial data 

FGDC