By the mid-1920s, major league clubs were beginning to develop "farm systems", that is, minor league teams owned or controlled by them, at which they could develop young prospects without the risk of the players being acquired by major league rivals. The pioneer in this development was Branch Rickey, who then ran the St. Louis Cardinals. As the 1921 National Agreement among the major and minor leagues which implemented Landis's hiring lifted a ban on major league teams owning minor league ones, Landis was limited in his avenues of attack on Rickey's schemes. Developing talent at little cost thanks to Rickey, the Cardinals dominated the National League, winning nine league titles in the years from 1926 to 1946.