The California Digital Newspaper collection, created and made available by the University of California, Riverside, is an outstanding resource. It has about 40 different newspapers, starting from the 1840s. Also, in my opinion, the scanning quality is quite good.
If you have California ancestors/relatives and wish to search for articles about them, I encourage you to make use of this free resource.
Also, I would encourage you to view this short video which demonstrates the navigation for this site. Navigation is quite easy, but there are some interesting anomalies and features of this site that you will want to be aware of.
The direct link for the site is: California Digital Newspaper Collection