Though Texas was a burgeoning state, home to some of the largest population centers of the United States, the climate of Texas, often arid on one end, and impossibly muggy on the other, had populations slowly migrating to better areas. It did not help that the Texas always had an ambivalent relationship with the rest of the US, and was perfectly willing to be the lone wolf in the downfall of civilization. It didn't take took long for various tribes to pick the state apart, piece by piece. Now Texas is no longer a state with easily defined borders, but a region that is vaguely said to start somewhere afterRed River, and end somewhere on the Rio Grande.
Right now, it's a microcosm of America in general, splintered between the farmers, the herdsmen, and the irrigators. The farms of the coast, that reach from Corpus Christie to Dallas are subjugated by the Anderson clan. The cowboys believe the farmers are an inferior, filthy people, but they serve their purpose as traders, and a large enough population for skilled laborers and artisans. Basically, the farmers serve as a pool of resources--more sophisticated weaponry, armor, wagons, as well as a surplus of calories to build up the Anderson army, building them up to have total domination of the southern plains.