Many Major League cities held two teams in those early days. Boston had the Red Sox and the Braves. Philadelphia had the Philllies and A's. Chicago of course, the Cubs and White Sox and New York had 3 teams with the Giants, Yankees and Dodgers. St. Louis was the 5th American city to host two Major League franchises with the Browns and Cardinals. Arguably there are still 5 cities today hosting two pro teams with NY, Chicago, L.A. and the Bay Area of California... and Baltimore/D.C. as the Washington Nationals are well within the Orioles jurisdiction and had to come to some
  financial understandings before the Orioles would allow them play in RFK (and Nationals) Stadiums. (In fact, the Orioles are still grumbling about it...).