How did California population become diverse?

In my opinion, it started with the gold rush in the 1840s and 1850s, which brought many over from many parts of the United States, its location, even today, allows many from that side of the world to come over, thus the reason why it has more Japanese immigrants on average. its also a large state, so near the bottom, its reasonably close to Mexico, so many immigrants come in through there, seeing how its so close by.