Minor League Baseball

The earliest professional baseball league, the National Association of Professional Base Ball Players of 1871 to 1875, commonly referred to as the National Association, comprised all fully professional teams. This system proved unworkable, however, as there was no way to ensure competitive balance, and financially unsound clubs often folded during the season. The National League (NL) was founded in 1876 with a limited membership which excluded less competitive and financially weaker teams, allowing for the most prosperous teams to compete against each other. Professional clubs outside the NL responded by forming regional associations of their own. There was a series of ad hoc groupings, such as the New England Association of 1877 and the Eastern Championship Association of 1881. These were loose groups of independent clubs which agreed to play a series of games over the course of one season for a championship pennant.

The first true minor league is traditionally considered to be the Northwestern League of 1883 to 1884. Unlike the earlier minor associations, it was conceived as a permanent organization. It also, along with the NL and the American Association (AA), was a party to the National Agreement of 1883. Included in this was the agreement to respect the reserve lists of clubs in each league. Teams in the NL and the AA could only reserve players who had been paid at least $1,000. Northwestern League teams could reserve players paid $750, implicitly establishing the division into major and minor leagues. Over the next two decades, more minor leagues signed various versions of the National Agreement. Eventually, the minor leagues allied to negotiate jointly.

In the late 1890s, the Western League run by Ban Johnson decided to challenge the NL's position. In 1900, he changed the name of the league to the American League (AL) and vowed to make deals to sign contracts with players who were dissatisfied with the pay and terms of their deals with the NL. This led to a turf war that heated up in 1901 enough to concern Patrick T. Powers, president of the Eastern League, and many other minor league owners about the conflict potentially affecting their organizations. Representatives of the different minor leagues met at the Leland Hotel in Chicago on September 5, 1901. In response to the NL–AL battle, they agreed to form the National Association of Professional Baseball Leagues (NAPBL), sometimes shortened to National Association (NA), which would later adopt the trade name "Minor League Baseball". The purpose of the NAPBL at the time was to maintain the independence of the leagues involved. Several did not sign the agreement and continued to work independently. Powers was made the first president of the NAPBL, whose offices were established in Auburn, New York.

In 1903, the conflict between the AL and NL ended in the National Agreement of 1903, which created the National Baseball Commission to oversee the major and minor leagues. The NAPBL became involved in the later stages of the negotiations to develop rules for the acquisition of players from their leagues by the NL and the AL. The 1903 agreement ensured that teams would be compensated for the players that they had taken the time and effort to scout and develop, and no NA team was required to sell their players, although most did because the cash was an important source of revenue for most teams. The NA leagues were still fiercely independent, and the term minor was seldom used in reference to them, save by the major-market sportswriters. Sports news, like most news generally, often did not travel far in the days before radio and television, so, while the leagues often bristled at the major market writers' descriptions, they viewed themselves as independent sports businesses. Many baseball writers of that time regarded the greatest players of the minor leagues, such as Buzz Arlett, Jigger Statz, Ike Boone, Buddy Ryan, Earl Rapp, and Frank Shellenback, as comparable to major league players.

The official relationship between the minor and major leagues was challenged throughout the existence of the Federal League. The league, an upstart challenger to the traditional major leagues, would frequently "raid" the minor leagues for talent throughout its brief existence. Certain member teams of the minor leagues advocated abandoning their relationship with the American and National Leagues to join the Federal League; however, this was rendered moot after the Federal League folded in 1915.

The relationship between the minor and major leagues again came into question following the First World War. In 1918, many minor leagues cut their seasons short due to players leaving for war. The major leagues did not shorten their seasons but did similarly struggle with player shortages. As such, the Commission allowed major leagues to sign minor-league players for the duration of the season.

However, a dispute arose about the rights to minor-league players following the 1918 season. Several major-league clubs claimed ownership over temporarily signed players, while their former minor-league clubs still claimed control. Notably, pitcher Jack Quinn was involved in a rights dispute. He had played for the Chicago White Sox in 1918 after the end of the Pacific Coast League season. After the season, his club, the Vernon Tigers, sold his rights to the New York Yankees. The White Sox, however, claimed to retain his rights. The Commission ultimately sided with the Tigers and Yankees. However, the incident severely damaged league-wide confidence in the Commission, serving as a factor in the eventual dissolution of the National Commission and creation of the office of the Commissioner of Baseball.

In 1921, Major League Baseball and Minor League Baseball signed an agreement allowing Major League teams to own Minor League teams. St. Louis Cardinals executive Branch Rickey used this agreement to develop a farm system for his team, purchasing lower-level clubs and using them to develop prospects prior to debuting in the Major Leagues. Commissioner Kenesaw Mountain Landis initially resisted Rickey's plan but, ultimately, the Great Depression drove teams to establish systems like Rickey's to ensure a steady supply of players, as many NA and independent teams could not afford to keep their doors open without the patronage of Major League Baseball. The leagues of the NA became subordinate to the major leagues, creating the first minor leagues in the current sense of the term. With the exception of the Pacific Coast League (PCL), which under its president Pants Rowland tried to become a third major league in the Western states, the other leagues maintained autonomy in name only, being totally economically dependent upon the AL and NL.

The 1922 Supreme Court decision Federal Baseball Club v. National League (259 U.S. 200), which grants baseball a special immunity from antitrust laws, had a major effect on the minor leagues. The special immunity meant that the AL and NL could dictate terms under which every independent league did business. By 1925, major league baseball established a flat-fee purchase amount of $5,000 for the contract of any player from an NA member league team. This measure was leveled primarily at the Baltimore Orioles, then a Triple-A team that had dominated the minors by keeping players longer than many competitors, allowing the players to more fully develop, driving up their sale value to major-league teams and giving Baltimore a talent advantage. Deprived of this option by the flat-fee policy, minor-league teams had little choice but to sell players as soon as they drew major-league interest.

Although the 1922 decision essentially guaranteed Major League financial dominance over the Minor Leagues, there was still resistance to the development of the farm system. Kenesaw Mountain Landis, Commissioner of Baseball, was reportedly "never a fan of the farm teams owned by major-league teams." Landis released numerous baseball players to free agency following perceived abuses of the farm system. For example, in 1930, Landis released Fred Bennett to free agency after the St. Louis Browns sent him to play in their farm system for a third consecutive year, then seen as a violation of the player's rights. This would lead to a legal battle with a court voiding the "secret absolute control" of players in 1931 without eliminating the farm system. However, later rule changes by the owners would formalize and limits major league clubs' ability to "option" players to the minors. Such rule changes largely voided the 1931 decision within the next few years.

Landis continued to fight to limit the extent of major-league control over the minor leagues, frequently seeking to curb unofficial affiliation and club control. Following an investigation of six teams in the St. Louis farm system in 1938, Landis ultimately released 74 players to free agency and fined the Cardinals $2,176, citing that the teams in question "were merely adjuncts to the St. Louis system." On similar grounds, he released 90 Detroit Tigers minor leaguers in 1939.

Minor League Baseball would peak in popularity in the years after World War II. In 1949, 448 teams played across 59 leagues in Canada, Mexico, and the United States, with all minor leagues combining for 39 million attendees that year. However, the rise of television in years after led to many minor-league clubs losing supporters for now-watchable major-league teams. Minor-league teams maintained territorial rights and had the option to refuse to let MLB teams air on television in their territory. Fearing insolvency, MiLB agreed to allow MLB to air on television in their territory in exchange for a share of television profits and financial support.

In 1962, MLB and MiLB agreed to terms that would largely end minor-league independence: major-league clubs would sign player development contracts (PDCs) with minor-league teams, requiring that a major-league club provide a full team of players to its minor-league affiliate and pay player salaries in exchange for full control over the players. With this, minor-league teams were essentially required to hand over control of their rosters to MLB partners. Though only a few minor-league clubs are directly owned by MLB teams, every MiLB team today requires a major-league affiliate.

Minor League Baseball's popularity would recover in the 1990s and continue to grow throughout the 2000s, reaching a new peak attendance of 41.6 million in 2009. In 2021, MiLB saw its size significantly reduced when MLB disaffiliated itself from nearly a quarter of all MiLB clubs and eliminate several levels of minor-league play.