I would assume that if it ever happens, it would break into two states: Northern California and Southern California, divided roughly at the 36°30' North paralle

I would assume that if it ever happens, it would break into two states: Northern California and Southern California, divided roughly at the 36°30' North parallel, keeping existing county borders. That would place San Francisco, Sacramento, Monterey and Fresno in Northern California, and Los Angeles, San Diego, and Bakersfield in Southern California. https://en.m.wikipedia.org/wiki/Parallel_36°30′_north https://en.m.wikipedia.org/wiki/Parallel_36°30′_north