Geologic maps of the United States are mainly produced at the state and federal levels. The Library collects maps from state geological surveys, the California Division of Mines and Geology, (now the California Geological Survey), and the U.S. Geological Survey. Closer to home, we have all of the sheets published by the Dibblee Geologic Foundation.
Maps produced by many of these agencies are now available online through the California Geological Survey and a database of the USGS and the Association of American State Geologists (AASG), the National Geologic Map Database.
More information on individual state geological surveys can be found on the AASG website.
Our collection of foreign geologic maps is also extensive but tends toward smaller scale maps. If we don't have what you need we're happy to direct you to sources outside of our collection to assist you in your research.