The coming of salaried players, of course, led to the original baseball “grounds” or fields (which were just that, without any of the amenities we’ve come to expect from our modern facilities) giving way to the ballparks and (eventually) stadiums of today. How do owners maintain facilities and teams pay their players? Charge admission! How are the spectators who bought tickets kept separate from nonpaying enthusiasts? By building walls and gates around the diamond.