High Quality Content by WIKIPEDIA articles! In Major League Baseball, the American League Championship Series (ALCS), played in October, is a round in the postseason that determines the winner of the American League pennant. The winner of the series advances to play the winner of the National League Championship Series in baseball`s championship, the World Series. On October 18, 2012, the Detroit Tigers swept the New York Yankees 4 wins to 0 to win the 2012 American League Championship, the Tiger`s eleventh American League Championship in their storied history.