There wasn't any sort of a war in which the United States captured or took California from Mexico after fierce battles in California itself; we just walked in. History books talk about California being ceded to the Us after the war in 1847 - 48 but the reality is that Comanches had prevented any meaningful Mexican presence in California until the 1840s, and then Anglos just walked in. There werer no more than a couple of thousand Mexicans in the place at that time. The state began to be settled after the arrival of the railroad in the 1860s and 70s.
Thanks for all of that valuable information about what truly happened.