Can you tell me more about what you're looking for?

If a site like OAC isn't giving you any results that you can work with, I'm afraid you might not find satisfactory results on other sites either. What specifically are you finding to be clunky? How can I help? Maybe your search terms need some troubleshooting?

• Are your search terms way too broad or way too specific? Try being either a bit more specific or a bit more generalized.

• Search for key words. Figure out who were some of the major players in the stuff you're interested in--search specifically for each of those names. Figure the major events, the relevant ethnic groups, the relevant places, the names of relevant political parties, religions, social movements, etc., and search for each term alone. Maybe try different combinations.

• Are you being "creative" in your search terms?--namely, if you are searching for names (people or places), it's always possible that it's spelled multiple ways or the name changed over time.

• Browsing isn't a bad thing. Will browsing collections while narrowing the results by date span (or some other available filter) instead of using search terms help pinpoint what you're looking for?

• Find the right terminology. Does it seem like you're searching for something that doesn't have a very good set of search terms to describe it? Try to find a secondary source that encompasses the sort of thing you're looking for, look it up in a good university library catalog, and take note of the listed "subjects" associated with that book in the catalog entry--then try another search using those terms.

I wouldn't give up on OAC--it really is much better than what's available online for most states. Another site of online primary sources you might want to try is: http://www.calisphere.universityofcalifornia.edu/.

I think California's digital newspaper collection is quite good and worth using if you're doing any California history research. (It's free! And the keyword search function actually isn't terrible!)

There are massive amounts of free online primary sources available these days. (Shameless plug for the subreddit I mod: /r/digitalhistory . It's been quiet lately, but I intend to post more frequently soon, and I welcome posts from anyone with a cool online source to share.) You can find tons of material relating to California, but it might not be necessarily organized geographically. Some of the big sites to start when searching for US primary sources: Digital Public Library of America, the Library of Congress, or the New York Public Library.

If you're a student, definitely be sure to see what databases your institution's library is subscribed to. They should also have research librarians there who can help you discover what resources your library has available.

For searching collections only available in brick-and-mortar buildings and not online, a good spot to try is the National Union Catalog of Manuscript Collections: http://www.loc.gov/coll/nucmc/oclcsearch.html. It's like worldcat.org in that it's pulling information from hundreds of library catalogs, but it focuses on archival collections, and it seems like there's stuff there that isn't in worldcat. It's sometimes difficult to interpret the search results, but it's about as close of a universal US archives catalog that exists at present. As far as I can tell, however, it's not possible to narrow the search results by the location of the archival institution/library.

It definitely takes time, but if you want to be comprehensive, I'd Google search for the online catalogs of every California academic library, archives, or historical institution I could think of, and then search each catalog. (If you go this route, you'll definitely want to keep some sort of a research log or detailed notes or else you might go crazy.)