Until 1969, when there were no divisions, the team finishing with the best record in each league won that league's pennant and faced the other league's pennant winner in the Fall Classic.
As a result, the winners in each division were now required to play each other in a best-of-five Championship Series to determine who would advance to represent their respective leagues in the coveted World Series.
However, if the wild-card team and the division leader with the best record are from the same division, the wild-card team plays the next winningest division leader, and the remaining two division leaders play.