The League Championship Series (LCS) is 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 LCS comprises the American League Championship Series (ALCS) and National League Championship Series (NLCS).
The League Championship Series was created 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. Concomitant with this, both leagues formed Eastern and Western Divisions, the first-place teams from which faced off in the LCS.
For its first sixteen seasons, the League Championship Series were best-of-five, using the format in which the team without home field advantage hosted the first two games, and the team with it hosted the rest of the LCS, making it impossible for the disadvantaged 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 two games at home.
In 1985, the LCS was lengthened to best-of-seven games in the 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 disadvantaged team would have had more games played at home than on the road if the series ends in five games.
Until 1998, the home-field advantage in the LCS was allocated on a rotating basis between the two (and from 1995 through 1997, among the three) division champions; since 1998, that advantage is given to the team with the better regular season record, but the wild card team never gets home-field, regardless of regular season records.
As of 2021, all thirty MLB teams have reached the LCS at least once. The Houston Astros and Milwaukee Brewers are the only teams to have played in both the ALCS and NLCS. Five teams have never lost an LCS: the Colorado Rockies (won in 2007), the San Diego Padres (won in 1984 and 1998), the Miami Marlins (won as the Florida Marlins in 1997 and 2003), the Tampa Bay Rays (won in 2008 and 2020), and the Texas Rangers (won in 2010 and 2011). Out of this group, only the Marlins have won a World Series title; they did it both times they reached the NLCS.