Mexico and the United States went to war over a vast amount of terrain — what would amount to half of Mexico when it was all over, beginning of course, with Texas, which the United States annexed. The U.S. interest in expansion is very plain. Texas we wanted simply for its fine agricultural production, cotton in particular, which turned out to be the major commodity. California was the real goal in the far west — to have harbors on the Pacific and make ourselves a continental empire. We were not terribly interested in New Mexico, Arizona, Colorado, Utah and Nevada, all of which belonged to Mexico as well, but those territories needed to be conquered if we were eventually to connect the Atlantic to the Pacific by railroad, which was already a dream. From the point of view of Mexico, these lands were not of any great value, but they belonged to Mexico. The lands were theirs and had potential value in the future. They were not of immediate economic value, but Mexicans knew full well that Texas was a wonderful place for agriculture. The reports that came back suggested that Texas and California were potentially very rich provinces. I don't think either the U.S. or Mexico especially appreciated the desert. It wouldn't be until the advent of air conditioning that we would get excited about the desert country.
Mexico recognized that it needed to hold its northern frontier if for no other reason than to stop the U.S. from moving even closer to Mexico, then taking the next inevitable step of moving into Mexico City itself. There was a kind of domino theory at work here.
This was an extraordinarily remote area of the Mexican Republic. In those days, the population centers were actually the reverse of the way they are today. In 1821, when Mexico became independent of Spain, California was sparsely populated with something like 3,200 Mexicans. New Mexico, on the other hand, had a population of about 40,000 and was the dynamo of the northern frontier. Texas was also sparsely populated with about 2,500 Mexicans. The folks who lived in this frontier zone essentially lived in islands — enclaves unconnected to one another. There were no horizontal lines of communication across the Southwest. People who lived in San Antonio were more apt to think of Saltillo, Monterrey, and Mexico City than they were Santa Fe. People who lived in Santa Fe were unlikely to communicate with people living in San Francisco. The gulf between them was enormous.
