They can all say they're from Mars, that doesn't make it true. Midland is arguably the eastern edge of West Texas, and many would say it's too far east to be West Texas.
The great definer of West Texas was Walter Prescott Webb. He set the boundary at the 100th meridian, where rainfall drops to 15 inches a year or less. Or at least it used to--now I think that's Houston. You're making the relatively modern mistake of the physically far western part of the state: I'm further west than you so that's West Texas, when the defining attributes are as much cultural as physical: importance of ranch culture, late (1870 or later) settlement, low rainfall, plains, irrigation, late Comanche exodus, and, most of all, being the western place that east and central Texans moved to. I'd say that Midland and Odessa are probably the eastern boundaries of West Texas culture, and everything west of there is physically west, but too sparse and too Spanish to be West Texas, even though it's physically west. West Texas is the southern part of Plains culture that includes Montana and the Dakotas, Nebraska, eastern Colorado, western Oklahoma, eastern New Mexico, and West Texas. Which is not El Paso, which is in west Texas, but culturally El Paso.
