East-blowing pollution was a huge problem in early industrial London, where many American settlers came from. Whether or not there was a pollution problem where they later built cities, the meme of west=fancy, east=working class was ingrained. Certainly in places like East Palo Alto, the problem is not being downwind of something. It's just that the name "East" is a self-fulfilling prediction of being worse. It only takes a tiny nudge to tip the economic divide towards one side of town or the other.