GEON hosts a compilation of gravity data for the lower 48 states as well as a magnetic data set for North America that was compiled by USGS Geological Survey, the Geological Survey of Canada, and several Mexican organizations. These databases permit users to download data based on a bounding box of user-defined extent.
The Pan American Center for Earth and Environmental Studies (PACES) and GEON played a significant role in the compilation of gravity data for the lower 48 states. This effort has been conducted in close cooperation with the U. S. Geological Survey, the National Image and Mapping Agency, NOAA, and academic colleagues.
USGS Aeromag FAQ