turf wars are in San Fierro, after you finish the mission where you take over glen park, you can go to an area that is shaded a color besides green, cuz thats your color. kill a few of that colors gang members, and three waves of a big gang war comes. If you survive every one, you earn that turf and it turns from whatever color it was to green. Also, other gangs can attack your turf, and you must defend. I've only seen this in los santos.
-gtA5fan