Baja California Sur still isn't densely populated, so why not throw that in, too? Mexico didn't even give them statehood until 1974.
Believe it or not the Mexicans were able to keep us Gringos out of southern Baja during the Mexican War, mainly because for us it was a sideshow far removed from any supply lines. In any case, it was thought to be worthless desert. What is surprising is that we didn't use the Mexican border between Alta and Baja when it came time for the treaty. Mainly that was because we weren't certain if San Diego was north or south of that border and we definitely wanted San Diego for its harbor. However, if we had used the Mexican border between the Californias, Tijuana would be a US city with its suburb of Rosarito Beach being the Mexican border city.
I recall an interesting discussion of the status of Baja when I was in college in 1976. Mexico's balance of payments was a wreck and a peso devaluation was looming. Oil was newly discovered but not yet developed, and the US was reeling from the actions of the OPEC cartel. Border issues in SoCal were heating up. The hypothesis we debated was whether the US should provide a financial bailout of Mexico through a purchase of Baja and guaranteed prices for Mexican oil.
