California
There are scores of sub-themes (e.g., Civil Rights under Social Reform), and hundreds of individual topic areas (Black Panthers). Calisphere is organized by the libraries of the University of California. This seems a very large collection, but again, nothing in the way of family history databases.
Lastly, there is also the official site of the California State Archives housed by the Secretary of State. Very little of their material is available online, but there are some interesting collections here:
California government history is covered by pages devoted to Governors, legislative histories, and even the working papers of the 1878-79 California Constitutional Convention.
There's a collection of the Robert F. Kennedy Assassination Investigation Records
Family history researchers will find some useful resources at this site, such as:
More historical archives and research materials can be found at these excellent resources: