<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> The American League Championship Series (ALCS) is a best - of - seven series played in October in the Major League Baseball postseason that determines the winner of the American League (AL) pennant . The winner of the series advances to play the winner of the National League (NL) Championship Series (NLCS) in the World Series, Major League Baseball's championship series . </P> <P> It started in 1969, when the AL reorganized into two divisions, East and West . The winners of each division played each other in a best - of - five series to determine who would advance to the World Series . In 1985, the format changed to best - of - seven . In 1994, the league was restructured into three divisions, with the three division winners and a wild - card team advancing to a best - of - five postseason round, known as the American League Division Series (ALDS). The winners of that round then advanced to the best - of - seven ALCS . In 2012, the playoffs were expanded again so that two wild card teams face off in a one - game wild card round to determine which team advances to the division series, with the playoffs then continuing as it had before 2012 (though with the possibility of a fifth seed being in the playoffs and a fourth seed being out) after the end of the wild card round . This is the system currently in use . </P>

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