19th century The earliest classifications used in the minor leagues began circa 1890, for teams that were party to the National Agreement of 1883. • Class A: contracts and reserve lists protected • Class B: contracts and reserve lists protected, but a major league team could draft a player for a set price • Class C: contracts protected • Class D: contracts protected, but any higher class could draft a player for a set price • Class E/F: no protection
20th century After the National Association of Professional Baseball Leagues was founded in 1901, classifications were redefined: Draft fee set an amount for a team in a higher class to select a player; n/a for Class A as it would be up to each team to negotiate with an interested major league club. Protection fee reserved a player to a team, even after a contract expired, preventing the player for seeking employment with any other team. All minor leagues were classified, Double-A remained the highest level through 1945. • Class A1: added in 1936, between Class A and Class AA.
Postwar changes with the Triple-A
Montreal Royals in July 1946 In 1946, with the minor leagues poised for unprecedented growth, the higher-level classifications were changed. Class AAA ("Triple-A") was created and the three Double-A circuits (the
Pacific Coast League,
International League, and the
American Association) were reclassified into Triple-A. The
Pacific Coast League (PCL), which had been rated Triple-A since 1946, was the only minor league to obtain this classification, which it held through 1957. due to increasing television coverage of major league games and in light of the
Dodgers and
Giants moving to
Los Angeles and
San Francisco, respectively. By the end of 1963, only 15 leagues above Rookie-level survived in the United States and Canada.
Changes between 1963 and 2021 The minor league system that evolved following the 1963 reorganization remained in place through 2020, categorizing leagues into one of six classes: Triple-A (AAA), Double-A (AA), Class A-Advanced (High A or A+), Class A (Low A), Class A Short Season, and Rookie. Furthermore, Rookie was further informally subdivided into Rookie Advanced, complex-based Rookie, and international summer baseball. •
Triple-A: The American Association was revived as a Triple-A league in 1969 and flourished with the minor league baseball boom of the 1980s and 1990s. However, all of its teams were again absorbed into the International and Pacific Coast leagues in 1998 as part of a sweeping reorganization of the minors' top classification. The American Association and the International League also played an interlocking schedule during the late 1980s as part of the
Triple-A Alliance. The Mexican League was upgraded from Double-A to Triple-A in 1967. •
Double-A: In 1964, the South Atlantic League changed its name to
Southern League. In 1971, because of continued contraction (and Major League expansion) that left each circuit with only seven teams, the Texas League and Southern League formed the 14-team
Dixie Association. The arrangement lasted only for that season, and the records and history of the constituent leagues were kept distinct. In 1972, each league added an eighth team, rebalancing their schedules. The leagues subsequently returned to prosperity with the revival of minor league baseball that began in the 1980s. •
Class A: In 1980, the Western Carolinas League changed its name, reviving the historic South Atlantic ("Sally") League moniker. Additionally, over time, two more classifications evolved from Class A. Under the rules governing the affiliated minor leagues, these became separate classifications, despite the similarity in name: • Beginning in 1965,
Class A Short Season leagues played approximately 75 to 80 games per season, starting in mid-June and ending in early September, designed to allow college players to complete their college seasons in the spring, be selected in the
MLB draft in June, signed, and then immediately placed in a competitive league. The classification was eliminated prior to the 2021 season, with the
New York–Penn League and
Northwest League as the only active leagues at this level at the time of the reorganization. • The
Class A-Advanced classification, one rung below Double-A, was introduced in 1990 for the
California League,
Carolina League, and
Florida State League, splitting the Class A level even further. Entering the 2021 season, three new "High-A" leagues were introduced in replacement of prior leagues at this level. •
Rookie Advanced: The
Appalachian League and
Pioneer League were classified as Rookie Advanced leagues beginning in 1991. The players in these leagues were thought to be further along in their development than players in the pure Rookie leagues, and hence games were more competitive. Teams in these leagues were allowed to sell concessions and charge admission. In practice, many major league teams would have either one affiliate at this level or one affiliate in Class A Short Season but not both, making them
de facto equivalent. The Rookie Advanced classification was eliminated prior to the 2021 season. •
Rookie: In 1964, the Pioneer League stepped down from Class A to Rookie league status, and the first "complex-based" leagues, the
Sarasota Rookie League and the
Cocoa Rookie League, made their debuts. The Sarasota Rookie League underwent a name change to the Florida Rookie League in 1965 before becoming the
Gulf Coast League the next season. The Cocoa Rookie League lasted only one season, and the
Florida East Coast League of 1972, based in the same region of the state, also existed for only one year. In 1989, a counterpart to the Gulf Coast League, the
Arizona League, made its debut and it continues to operate as a Rookie-level league for MLB teams with spring training facilities based in Arizona. There were some failed start-up leagues. During the 1970s, three official minor leagues (members of NAPBL) attempted unsuccessfully to revive unaffiliated baseball (teams not associated with specific MLB franchises) within the organized baseball structure. These were the Class A
Gulf States League (1976) and
Lone Star League (1977), and the Triple-A
Inter–American League (1979). None lasted more than a full season.
Reorganization of 2021 In October 2019,
Baseball America reported that Major League Baseball had proposed dramatic changes to MiLB that would take effect after expiration of the Professional Baseball Agreement, which governed the MLB–MiLB relationship, at the end of the 2020 season. This included the elimination of many minor league teams. In mid-November 2019, more than 100 members of the
United States Congress signed a letter sent to
Commissioner of Baseball Rob Manfred opposing the proposal, noting that it "is not in the best interest of the overall game of baseball" and that it would "devastate our communities, their bond purchasers and other stakeholders affected by the potential loss of these clubs." On November 21, 2019, Minor League Baseball released a statement, asserting that it is "unnecessary and unacceptable to wipe out one-quarter of minor league teams" and characterized the proposal as a way "to improve the profitability of MLB". Manfred rebuked Minor League Baseball for releasing the negotiations to the public and threatened to cut ties with MiLB altogether. The following changes, which represent the first significant overhaul of minor league classifications since 1963, have since been implemented: • The
Major League Baseball draft was moved from mid-June to July to coincide with the
MLB All-Star Game, and reduced from 40 rounds to 20. • The Rookie-level
Appalachian League was converted to a
collegiate summer baseball league designed for rising freshmen and sophomores. • The
independent American Association,
Atlantic League, and
Frontier League and formerly Rookie-level
Pioneer League became MLB Partner Leagues, with the ability for MLB clubs to acquire players from the Partner Leagues to assign to affiliated clubs. • The
MLB Draft League, a "showcase league" for college players expected to be selected in the annual
MLB draft, was formed, with each team in the league playing a 68-game summer season. Four teams from the
New York–Penn League (
Mahoning Valley Scrappers,
State College Spikes,
West Virginia Black Bears, and
Williamsport Crosscutters), one from the
Eastern League (
Trenton Thunder), and one from the
Carolina League (
Frederick Keys) composed the initial league when it debuted in May 2021. • Three
independent league teams—the
St. Paul Saints, the
Sugar Land Skeeters (renamed the "Sugar Land Space Cowboys" in 2022), and the
Somerset Patriots—were brought into MiLB. The Skeeters became the Triple-A affiliate of the Houston Astros, the Saints became the Triple-A affiliate of the Minnesota Twins, and the Patriots became the Double-A affiliate of the New York Yankees. • The number of MiLB teams, not counting teams in the complex-based
Arizona Complex League and
Florida Complex League, both of which are directly owned by MLB, was reduced from 160 to 120. Short-Season A and Rookie Advanced leagues were eliminated. • The
New York–Penn League was shut down, leaving seven of its teams without an invitation to join another league. ;League changes The following teams lost affiliation during the 2021 realignment: ;League realignment On February 12, 2021, Major League Baseball announced new league alignments for all 120 affiliated Minor League Baseball clubs effective as of the 2021 season. Contrary to previously published reports indicating that realignment would retain the names of the existing minor leagues, Major League Baseball elected to abandon the names of existing minor leagues in favor of a new, class- and region-based naming system. Triple-A was divided into two leagues: •
Triple-A East, consisting of 20 teams aligned into three divisions (Midwest, Northeast, and Southeast). •
Triple-A West, consisting of 10 teams aligned into two divisions (East and West). Double-A was divided into three leagues: •
Double-A Central, consisting of 10 teams aligned into two divisions (North and South). •
Double-A Northeast, consisting of 12 teams aligned into two divisions (Northeast and Southeast) •
Double-A South, consisting of eight teams aligned into two divisions (North and South). High-A (formerly Class A-Advanced) was divided into three leagues: •
High-A Central, consisting of 12 teams aligned into two divisions (East and West). •
High-A East, consisting of 12 teams aligned into two divisions (North and South). •
High-A West, consisting of six teams without divisional alignment. Low-A (formerly Class A) was divided into three leagues: •
Low-A East, consisting of 12 teams aligned into three divisions (Central, North, and South). •
Low-A Southeast, consisting of 10 teams aligned into two divisions (East and West). •
Low-A West, consisting of eight teams aligned into two divisions (North and South). The US-based Rookie-level leagues were renamed prior to starting play in late June; the former Gulf Coast League was renamed as the
Florida Complex League and the former Arizona League was renamed as the
Arizona Complex League. On March 16, 2022, Minor League Baseball announced that the historic league names were acquired by MLB. The region-based names were scrapped and the previous league names given to the new leagues that most closely resembled the old leagues. • Triple-A East became the International League • Triple-A West became the Pacific Coast League • Double-A Central became the Texas League • Double-A Northeast became the Eastern League • Double-A South became the Southern League • High-A Central became the Midwest League • High-A East became the South Atlantic League • High-A West became the Northwest League • Low-A East became the Carolina League • Low-A Southeast became the Florida State League • Low-A West became the California League The Low-A classification was also renamed Single-A. Additionally, the International League was reorganized from three divisions to two: East and West. ==Organization==