<P> A structured playoff series began in 1969, when both the National and American Leagues were reorganized into two divisions each, East and West . The two division winners within each league played each other in a best - of - five League Championship Series to determine who would advance to the World Series . In 1985, the format changed to best - of - seven . </P> <P> The National League Championship Series (NLCS) and American League Championship Series (ALCS), since the expansion to best - of - seven, are always played in a 2--3--2 format: Games 1, 2, 6 and 7 are played in the stadium of the team that has home - field advantage, and Games 3, 4 and 5 are played in the stadium of the team that does not . </P> <P> MLB night games started being held in 1935 by the Cincinnati Reds, but the World Series remained a strictly daytime event for years thereafter . In the final game of the 1949 World Series, a Series game was finished under lights for the first time . The first scheduled night World Series game was Game 4 of the 1971 World Series at Three Rivers Stadium . Afterward, World Series games were frequently scheduled at night, when television audiences were larger . Game 6 of the 1987 World Series was the last World Series game played in the daytime, indoors at the Metrodome in Minnesota . (The last World Series played outdoors during the day was the final game of the 1984 series in Detroit's Tiger Stadium .) </P> <P> During this seven - year period, only three teams won the World Series: the Oakland Athletics from 1972 to 1974, Cincinnati Reds in 1975 and 1976, and New York Yankees in 1977 and 1978 . This is the only time in World Series history in which three teams have won consecutive series in succession . This period was book - ended by World Championships for the Pittsburgh Pirates, in 1971 and 1979 . </P>

List of how many world series each team has won