Minor League Baseball is a hierarchy of professional baseball leagues in the Americas that compete at levels below Major League Baseball (MLB) and provide opportunities for player development and a way to prepare for the major leagues. All of the minor leagues are operated as independent businesses. Most are members of the umbrella organization known as Minor League Baseball (MiLB), which operates under the Commissioner of Baseball within the scope of organized baseball. Several leagues, known as independent baseball leagues, do not have any official links to Major League Baseball.
Except for the Mexican League, teams in the organized minor leagues are generally independently owned and operated but are directly affiliated with one major league team through a standardized Player Development Contract (PDC). These leagues also go by the nicknames the "farm system," "farm club," or "farm team(s)" because of a joke passed around by major league players in the 1930s when St. Louis Cardinals general manager Branch Rickey formalized the system, and teams in small towns were "growing players down on the farm like corn."
Major League Baseball and Minor League Baseball teams may enter into a PDC for a two- or four-year term. At the expiration of a PDC term, teams may renew their affiliation, or sign new PDCs with different clubs, though many relationships are renewed and endure for extended time periods. For example, the Omaha Storm Chasers (formerly the Omaha Royals and Omaha Golden Spikes) have been the Triple-A affiliate of the Kansas City Royals since the Royals joined the American League in 1969, but the Columbus Clippers changed affiliations, after being associated with the New York Yankees from 1979, to the Washington Nationals in 2007 and have been affiliated with the Cleveland Indians since 2009.
A few minor league teams are directly owned by their major league parent club, such as the Springfield Cardinals, owned by the St. Louis Cardinals, and all of the Atlanta Braves' affiliates except the Florida Fire Frogs. Minor League teams that are owned directly by the major league club do not have PDCs with the parent club and are not part of the reaffiliation shuffles that occur every other year.
Today, 19 affiliated minor baseball leagues operate with 256 member clubs in large, medium, and small cities, as well as the suburbs of major cities, across the United States, Canada, Mexico, and the Dominican Republic. Several more independent leagues operate in the United States and Canada.
The earliest professional baseball league, the National Association of Professional Base Ball Players of 1871 to 1875, comprised all fully professional teams. This system proved unworkable, however, as there was no way to ensure competitive balance, and financially unsound clubs often failed in midseason. This problem was solved in 1876 with the formation of the National League (NL), with a limited membership which excluded less competitive and financially weaker teams. 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.