Texas, California, Nevada, Utah, most of Arizona, a little of Wyoming, part of Colorado, and half of New Mexico were annexed from Mexico. That is one reason why those states have such large Mexican populations to this day. But the Mexican population in those states was always very small to begin with...It was very sparsely populated. Most of the Mexicans were concentrated along the present day border in places like San Diego, El Paso, Tucson, San Antonio etc...    The reason those states have such large Mexican populations now is....you guessed it....illegal immigration.    And like our Korean friend said....most of the Mexicans in those regions were White (Spanish) Mexicans, not brown mongrels and indians.