Cities that hosted MLB teams from 1903 to 1953; cities that hosted one team are in red, cities that hosted two teams are in black. New York/Brooklyn, with three teams, is in orange. No major league baseball teams moved or were added between 1903 and 1953.
…The expansion of MLB coincided with an increase in the ease of travel by commercial jets, making it easier for players to fly across the continent. This is important given that when Walter O’Malley moved his Dodgers to Los Angeles, the closest team, other than the San Francisco Giants, was in St. Louis.
The expansion of baseball is also accompanied by the increase in popularity of television. Baseball expanded, in large part, because interest in the sport grew leading up to and during the 1950s and 1960s. In home televisions allowed for this increase in popularity and helped make New York’s pastime, America’s pastime.