Realignment

Realignment is the process by which the composition of a baseball league is modified for a reason other than expansion or contraction. In practice, realignment occurs when teams switch from one league to another.

At the major league level, realignment occurred regularly in the 19th century, a time when teams were often more viable entities than the leagues to which they belonged. A team would regularly move to another league which promised better financial returns. Thus, a number of the current National League franchises started in the American Association and were added to the senior circuit through a process of realignment. This stopped at the major league level following the contraction of four teams from the National League after the 1899 season and the creation of the American League in 1901. While there were a number of franchise relocations in the early years of the American League, and then in both leagues starting in the 1950s, the issue of realignment did not come up again until two rounds of expansion had added four teams to each major league in 1969, bringing them from 8 to 12 teams.

The first form of realignment was the 1969 splitting of the two major leagues into two divisions each, with the division winners playing each other in a League Championship Series. This format endured (with a few teams changing divisions in the AL between 1970 and 1972) through two more rounds of expansion, one in the AL in 1977 and the other in the NL in 1993. However, at that point, MLB decided to realign again by changing the divisional format starting in 1994, with the creation of a third division in each 14-team league. This in turn led to the creation of another round of postseason play, the Division Series and the addition of a wild card.

With MLB contemplating another round of expansion in the late 1990s, with one team to be added to each league, the issue of realignment became hotter, because the two leagues wanted to keep an even number of teams for scheduling purposes (interleague play was only introduced in 1997, and it was not certain at first that the innovation would be permanent). Because each team wanted one of the two new teams, something had to give. This was when a plan for Radical Realignment, which would have seen a number of teams switch leagues in order to reorganize them on a more logical geographic basis, began to circulate. In the end, the plan was too disruptive and failed, and instead, realignment only involved one team, the Milwaukee Brewers, who switched from the American League to the National League before the 1998 season, when the two latest expansion franchises - the Arizona Diamondbacks and Tampa Bay Devil Rays - began play.

Another round of realignment took place a decade and a half later. By then, interleague play had become an accepted feature of the baseball calendar, and MLB felt it was time to once again have two leagues with an equal number of teams, and six divisions also with an equal number of teams. This required one team to move from the NL to the AL, to give each league 15 teams. Milwaukee was not interested in switching back, so it was the Houston Astros who were convinced to switch leagues, doing so before the 2013 season. This latest realignment had another consequence, which was to force interleague play to take place during the entire season, and not just during a couple of blocks in the middle of the year as had been the case since 1997, so that all 30 teams could play games simultaneously.