We must remember that this southwestern part of "our" country - California, Nevada, Arizona, New Mexico, and Texas, and part of Colorado - used to be another country - Mexico. We went to war with Mexico, and as a result of the signing of the treaty of Guadalupe-Hidalgo, we moved the border of Mexico to the Rio Grande, thus taking about 1/2 of their country for our own. We "won" it.This is what happens when we don't teach history (or worse, teach the PC variant).
We paid for the land in question. We paid a total of $18 million dollars for the "Mexican Cession", $15 million directly to the government of Mexico and an additional $3 million of debt to American citizens was assumed. In addition, we paid $10 million for the "Gadsden Purchase", a small chunk of land that is now in southern Arizona and New Mexico. We overpaid for Gadsden because some felt that we had underpaid for the Cession...even though we paid even less for the Louisiana Purchase.
Oh yeah, we also did them the courtesy of giving back their national capital that we had captured in a war.
-Eric
Sad but true.