Every Major League Baseball team has a jurisdictional area. It is a radius of approximately 75 miles. In those 75 miles, no other professional Major or Minor League team can exist, that would detour the fans away from the pre-existing team in the area. The Minor Leagues have a jurisdiction as well. It is why the Southern League has a team playing in Zebulon (of all places)... because it is the first city located outside of the Triple-A Durham Bulls radius (which is also why a town as huge as Raleigh doesn't own a professional affiliated ballclub).