Digital state geologic maps
The USGS has created a page to pull together information and give access to all of the states’ geologic maps. The page lists each state and then gives basic information about the digital map, the source map, and comments. It is not always easy to find out what format the digital map is in, but most seem to be in ArcInfo export format or ArcGIS shapefile format. The larger goal is “to create a small-scale integrated bedrock-oriented geologic map database of the U.S. based on digital state geologic maps.”