Statewide registration of deaths was made mandatory in California in 1905, with most counties complying with the registration requirement by 1920. While that requirement has made it relatively straightforward if you are looking for a California death record from the 20th century, it probably doesn't help you if the record you are after dates from before registration was made mandatory. If you are searching for a particularly old death record, however, there are places that may prove helpful. We will look at just a few of those places below.
While statewide registration of deaths only became law in 1905, that doesn't mean that individual counties weren't registering their own deaths before that date. County records are a great resource for finding local death records, some of which may date to the 19th century. Unfortunately, many county records remain offline, meaning that to find out if such records exist you will have to contact your county courthouse.
Perhaps a more obvious place to look for a record of a deceased person is through cemetery records. In recent years, FindaGrave.com has become the go-to place for searching an online database of cemetery records. Many Californian graves are listed on the site. Of course, one drawback of this approach is that not all cemeteries will be listed. Furthermore, gravestones from the 19th century may have become damaged and illegible.
Missionaries have been coming to California since the 18th century and they have left behind them relatively well-kept records. Generally, Roman Catholic death records are the most reliable, since Catholic missions have been present in the state for centuries. Many Archdioceses maintain records of parishioners' deaths going back well into the 19th century. Other churches, notably the Lutheran, Methodist, Presbyterian, and Mormon churches also have decent archival records that can be searched, although not all will be online.
Newspapers had been thriving in California since at least the mid-19th century, which makes newspaper obituaries an excellent resource for finding death records from prior to 1905. Libraries, of course, will have newspapers archived and are generally your most reliable resource for such information. The California Digital Newspaper Collection is also a handy resource. It features freely accessible California newspapers dating back to 1846 which have been scanned and made available online.
Finally, wills and probate records may be useful, although they can be trickier to find. A paid subscription to Ancestry.com will provide access to quite a few probate records. Of course, this will cost money, but it's a good choice if any of the other avenues you have pursued have failed to produce much information. Furthermore, if you are looking to delve into your family history then last wills and testaments have the added benefit of providing an intimate window on your ancestors' lives (something that a death certificate alone cannot provide).
California was once part of the Wild West, so it shouldn't be all too surprising that death records from the 19th century are spotty at best. However, as the above article shows, if you are looking for a death record from prior to 1905 then you have a number of options that should help you in your search.