There are six divisions in MLB, with three each in the National League and the American League.
Specifically, each of the two Major Leagues is divided into three geographically-distributed divisions:
Each of these six divisions is home to five teams, accounting for all 30 Major League clubs.
But the current structure has been in place only since 2013 and, the majority of MLB history through 2020 has been played with no divisions at all.
History of MLB Divisions
From the inception of the American League in 1901 through the 1968 season, MLB consisted of two leagues, generally with 8-10 teams each.
The exception to this rule came during 1914 and 1915, when the Federal League joined the Majors, yet didn’t participate in the World Series.
During those nearly seven decades, all games were played between teams in the same league, and the team with the best record in each league won the pennant for that season.
The two pennant winners then squared off in the World Series.
In 1969, after a decade of expansion activities and with four new teams slated for the upcoming season, baseball split into divisions for the first time.
Each of the two leagues was divided into an East and West division, with six teams in each, adding up to 24 teams total.
The season-long champion of the East Division in each league played the season-long champion of the West Division in the same league to determine the pennant winner, squaring off in the League Championship Series.
Then, as before, the two pennant winners played each other in the World Series.
The first four division winners, in that 1969 season, were:
- American League East: Baltimore Orioles
- American League West: Minnesota Twins
- National League West: Atlanta Braves
- National League East: New York Mets
The Orioles beat the Twins in the first ALCS, while the Mets defeated the Braves in the NLCS.
Then, the so-called Miracle Mets, a 1962 expansion team, took the World Series from the Orioles.
(That Mets team, by the way, is often credited with helping to spawn the modern bullpen by moving to a five-man rotation.)
The MLB divisional structure remained unchanged until 1977, when the expansion Toronto Blue Jays joined the American League East and the Seattle Mariners joined the American League West.
That made for an uneven balance, with 14 teams in the A.L. and 12 in the N.L., but nothing else changed in terms of the basic playoff structure or who teams played — all games remained intraleague affairs.
Even More Expansion
The situation remained unchanged until 1993, when the expansion Colorado Rockies and Florida Marlins joined the N.L. West and N.L. East, respectively, to leave MLB with four seven-team divisions.
Before the next season, baseball realigned to the current six-division format, with three in each league.
However, with 28 teams, that meant four divisions would have five teams, and two — the West Divisions — would have only four.
In order to accommodate champions across all six divisions, baseball expanded its playoffs for 1994. Each league would see the three division winners plus one wild card team in the postseason.
However, due to the player strike that summer, the entire 1994 postseason was cancelled, and the first wild card games took place in 1995.
Partially due to the uneven distribution of teams across divisions and partially due to desire to develop more natural geographic rivalries, MLB adopted a slate of interleague games for the first time in 1997.
It was a prelude to more changes on the horizon.
The 1998 season brought two more expansion teams, the Arizona Diamondbacks and the Tampa Bay Devil Rays.
Arizona slotted into the NL West, but the Devil Rays joined the AL East.
Meanwhile, the Milwaukee Brewers moved from the AL Central to the NL Central, and the Detroit Tigers moved from the AL East to the AL Central.
That left the NL Central with six teams and the AL West with just four.
That structure remained in place until the Houston Astros moved from the NL Central to the AL West before the 2013 season.
Through 2020, no other divisional restructuring has occurred, though MLB has continued to expand its playoffs.
As of 2021, each league sends the three division winners and two wild card teams to the playoffs each year.
Most Division Titles
Through 2020, the Atlanta Braves have won 20 division titles, more than any other team.
Of those titles, five came in the old National League West, and 15 have come in the National League East.