I am not in California. I just happened to see your post when I was posting in the California, Santa Barbara Co. message board. I am a librarian and archivist by training.

The answer depends upon what you wish to do.

Do you wish to make a trip/visit to an actual library/archives/museum to go through the microfilmed old newspapers for places in California? If so, first I suggest you contact (with a phone call) the California State Library and ask to talk with one of the reference librarians there. He/she can direct you better than I can.

This is the main phone number: (916) 654-0261. Days/hours of service: Monday – Friday, 8:00 am – 5:00 pm (Pacific Time)

This is the web page address for the California State Library page with info on their Calif newspaper collection: http://www.library.ca.gov/calhist/newspaper.html

If you do not wish to actually go to the location with the largest collection of Calif. newspapers, then, you may be interested in the California Digital Newspaper Collection, which is accessible electronically and remotely through the Internet.
This is the web page link that tells about the collection:
http://cdnc.ucr.edu/about_us.html

This is the link to register (free) to log in to access the Calif. Digital Newspaper Collection (copy the web address and paste it into your browser search box):
http://cdnc.ucr.edu/cdnc/cgi-bin/cdnc?a=a&command=ShowAu...-----

Another remote, electronic option is if your local public library system subscribes to databases of old newspaper articles (indexed & full-text.) The databases of old newspaper articles my local public library system subscribes to and allows to be searched & viewed by logging into my library borrower account through the library web pages are:
Access NewspaperArchives
Nineteenth Century U.S. Newspapers

To find out what databases your public library has available, I recommend you telephone your local public library and ask a reference librarian. It may be a good idea to plan a visit to your local public library so one of the librarians can give you some initial one-on-one instruction on the best search strategies to use when you do access the databases remotely.

Hint: Probably the reference librarians at your public library (or college/university library if you are a college/univ. student) could have given you this same info. :-) Don't forget to use their services, which you have already paid for (as a taxpayer or as a college/univ. student.)