In the first ever League Championship Series playoff game on October 4, 1969, the Mets beat the Braves 9-5 in Atlanta.
The League Championship Series is the official name for the semifinal round of postseason play in Major League Baseball which has been conducted since 1969. In 1981, and since 1995, the two annual series have matched up the winners of the Division Series, and the winners advance to meet in the World Series
The League Championship Series was promulgated in 1969, when both the National League and the American League increased in size from ten teams to twelve with the addition, via expansion, of the Montreal Expos and San Diego Padres to the former and the Kansas City Royals and Seattle Pilots (now the Milwaukee Brewers of the NL) to the latter. As a result, both leagues formed Eastern and Western Divisions, the first-place teams from which faced off in the LCS.
Originally, the League Championship Series were best-of-five using the 2–3 format in which the team without home field advantage hosted the first two games and the team with it hosted the remaining game(s), making it impossible for the disadvantage team to win the series at home. It also allowed those teams the unusual luxury of starting a series at home, possibly having home field advantage in a three-game series, and a guarantee that they play the maximum number of games possible at home .
In 1985 the LCS was lengthened to best-of-seven games in the 2-3-2 format with the team holding home-field advantage opening the series at home and playing the next three games on the road, before returning home for two more possible games. The disadvantage team would have had more games played at home than on the road if the series ends in five games.
As of 2016, all 30 MLB teams have reached the LCS at least once.