A chant used to justify illegal immigration from south of our borders.
All well and good. But, let's examine the truth of this statement.
When did Spain or later Mexico ever truly “control” land in these states? From the very beginning, Spain never had complete military control of Texas, Arizona, or New Mexico. For this entire area, there were never more than two or three hundred poorly armed and ill-equipped soldiers in scattered garrisons or presidios. And, those few garrisons relied heavily on support from missions established by Catholic missionaries.
Let's take California as an example. Up to 1769, all Spanish efforts were guided by the Jesuits in Lower California, their widely scattered missions manned by groups of no more than five soldiers at each. There was a “presidio” - a poorly manned garrison – at San José del Cabo put there as it was the main shipping point in to and out of Lower California.
When Father Serra and Governor Gaspar Portolá reached the future site of San Diego, it was with a military compliment of less than 100 soldiers fit for duty. Of the 30 Catalonian Volunteers, only six or seven did not suffer from dysentery and diarrhea. Even the hardy Leatherjacket Soldiers faced physical problems. 100 hundred soldiers to cower 60,000 Iron Age savages!
And, the California Indians no longer owned anything as they had been all but wiped out when the missions fell into ruins. Those few surviving peones struggled, poorly clad and barely fed.
So, let me ask this question – if Mexico didn't bother to man its outposts or seriously control the vast territory of California [which included Arizona and New Mexico] knowing it was so sparsely settled that it did not merit the status of being a state, why should the belief continue that those areas still “belong” to Mexico? And thereby justifying to incursion of Mexican citizens without legal documents?