The Online Archive of California (OAC) provides free public access to detailed descriptions of primary resource collections maintained by more than 200 contributing institutions including libraries, special collections, archives, historical societies, and museums throughout California and collections maintained by the 10 University of California (UC) campuses.

The OAC includes extensive material relating to Sonoma County history.

Collection guides unlock archive, library, and museum doors.

Access to collection guides (also known as finding aids) is essential to your understanding of a collection's content and for determining whether it is likely to satisfy your research needs.

The OAC's comprehensive online collection guides make it easy to find collections and locate individual objects. These guides provide detailed descriptions of the items in a collection, as well as background, historical studies, and analyses (when available). Selected items have been digitally scanned for immediate online viewing.

Do you have a question about a collection or item, or would you like to view the original materials? Are you seeking permission to publish or reproduce an image or text? OAC collection guides also provide contact information for the institution that maintains the resources: you can connect with a librarian, archivist, or curator in order to learn more about and gain access to the physical materials.

OAC is a vital resource for researchers.

As California's central repository for collection guides, the OAC is a vital resource that serves everyone interested in California's rich collections: browse online, search for information about specific items and their location, and learn how to access them. New technology solutions enhance discovery, making it easy to locate specific items quickly or browse collection contents online.