MLB Roster History - Baseball Almanac

The 25-Man Roster | 1884-2020:

Once considered the active roster, the 25-man was composed of 25 players who are playing for their Major League team. They were the starting eight position players, pitchers, and reserve players on the team. Players on the active roster were also on the 40-man roster. These players were generally the only ones who dressed in uniform and the only ones who may take the field in a game at any time. Typically, only players on the 25-man roster, and players who are on the disabled list but were on the 25-man roster, travel on road trips with the Major League team.

Typically, a 25-man roster would have consisted of five starting pitchers, seven relief pitchers, two catchers, six infielders, and five outfielders. In the American League a full-time designated hitter is usually classified as either an infielder or an outfielder, not a DH, because most DHs do play first base, left field, or right field from time to time.

Starting with the 2012 season, teams were allowed 26-man rosters for "day-night" doubleheaders—two games scheduled on the same day, but with the stadium cleared between games, and separate tickets sold for each game—as long as the doubleheaders have been scheduled with at least 48 hours notice.

The active roster has evolved over time and a few years of note include:

1881: The roster was set at 11 players. A few years later, it was increased to 14.

1884: The roster was set at 25 players to keep players from signing with the "outlaw" Union Association.

1892: Each team started the season with 15 players, but in mid-June the National League reduced the official roster size down to 13.

1901: When the American League declared itself a major league, they set their roster size to 18 to draw more players from the National League, but reduced it down to 14 in May (which was equal to the National League). They increased it to 16 in 1904, and 17 in 1905.

1910: Both leagues set their roster size at 25 beginning May 15 until August 20. Teams were able to have 40 players under their control originally, decreased the next year to 35. World War I, World War II, the Depression, and a few other historical events altered roster sizes, but the traditional 25 was now set.

1914: Roster Limits were eliminated for one year due to the challenge by the Federal League, and the National League reduced its roster sizes for the next 4 years.

1919: Active rosters returned to 25 from May 15 to August 31, and 35 the rest of the season, increasing to 40 in 1921. This remained the standard until 2020 except for adjustments made due to the Depression and World War II.

1957: The active roster for the first month of the season was reduced to 28.

1968: The active roster could only be 25 from the start of the season until September 1.

2020: The active roster was increased to 26 players from the start of the season until September 1, and reduced to 28 from September 1 till the end of the season, although the rule was tweaked in 2020 due to the global COVID-19 pandemic.

The Active Roster | 2020-Today:

Also called the 26 man roster, the active roster is composed of 26 players who are eligible to play for their Major League Baseball team. They are the starting players and reserve players on the team. Players on the active roster are also on the 40-man roster.

Teams must have a minimum of 25 players on their active roster at any time. Typically, only players on the 26-man roster, and players who are on the disabled list but were on the 26-man roster, travel on road trips with the Major League team.

At present, active rosters may be increased to 28 players from September 1 to the end of the season. Since the 2020 season, teams have been allowed 27-man rosters (29 after August 31) when they play two games in a day—as long as they have been scheduled with at least 48 hours notice.

The 40-Man Roster | Reserve List:

Also called the reserve list, the 40-man roster is composed of all the players in a Major League club's organization who are signed to a major-league contract. These are the players who are able to be called up to the 26-man roster at any given time. If a club wishes to add a player not on its 40-man roster to its active roster, it must first remove another player from the reserve list.

Also on the 40-man are any players on the 10-day injured list and minor league players who are signed to a major-league contract, but are on an "optional assignment" to the minors. (Each player has three "option years" to be sent to the minors once on the 40-man before they must be placed on waivers to be sent there.)

Players who were on the 40-man roster, but are placed on the 60-day injured list are taken off the 40-man until the time on the DL is over. The same applies to players who are suspended. Because players on the 60-day IL are taken off the 40-man with no risk of losing the player, MLB teams often transfer injured players from the 10-day IL to the 60-day IL so that they can add another player to the 40-man without having to designate a player for assignment. Designating for assignment is the removal of a player from the 40-man, whereby the team has 10 days to trade the player, release him, or send him to the minors.

Postseason Roster:

A postseason roster takes effect only if a team clinches a playoff berth. Players who are part of the team's 40-man roster or the 60-day IL on August 31 are eligible to participate in the postseason. The one exception is for replacing players on the disabled list. Any injured player who is eligible for postseason play may be replaced by any player that was on an active or disabled list for either that team or any of its affiliated minor league teams at midnight August 31 with permission of the commissioner's office.

Only 26 players can be placed on a postseason roster. Other players who are not on the 26-man active roster will be placed on the secondary squad. Players who are on the disabled list or any other non-active transaction by the end of the regular season will have their transactions passed on in the postseason. Rosters for a series are set at the beginning of the series and no changes to the 26-man active roster are allowed except when a player is moved to the disabled list or any other inactive transaction.

If a player is moved to the disabled list or another inactive transaction during a series, he then becomes ineligible to be returned to the 26-man active roster for the remainder of the series as well as the next series if applicable. If any player goes on any inactive transaction, any player from the secondary squad can be promoted to the 26-man active roster for the remainder of the series if applicable.