Well, I didn't bring it up, but you really should read a little history. Texas/Tejas was an separate entity under Spanish rule, but the new Mexican government incorporated it into the next state south (Coajila) and the state capitol was moved south about 500 miles when Mexico gained its independence. Immigration from the US was encouraged, because very few Mexicans wanted to move to the far frontier. Most of the agreements with immigrants were abrogated in 1830, which is what eventually led to the Texas War of Independence. Texas was incorporated into the US about 10 years after its war with Mexico, and it was the failure of the US and Mexico to agree on its southern boundary which precipitated the Mexican-American War.