 The Giants and A's enjoyed a limited rivalry at the start of the 20th century before the Yankees began to dominate after the acquisition of Babe Ruth in 1920, when the Giants were in New York and the A's were in Philadelphia.The teams were managed by legendary leaders John McGraw and Connie Mack, who were considered not only friendly rivals but the premier managers during that era, especially in view of their longevity (Mack for 50 years, McGraw for 30) since both were majority owners.Each team played in five of the first 15 World Series (tying them with the Red Sox and Cubs for most World Series appearances during that time period).