How Baseball Handled the Growing Popularity of Football
Due to the growing popularity of pro football, the MLB felt it needed to expand in order to keep up with the growing demand for football. The league felt that it needed to reclaim its spot as America's national past time. In 1969 the league added four franchises which were located in Kansas City, Montreal, San Diego, and Seattle. Although these franchises struggled in the beginning, eventually they were able to become established members of the MLB.
Links For Further Reading and Baseball Nerds
A Hardball Times Summary