Minor leagues are professional sports leagues which are not regarded as the premier leagues in those sports. Minor league teams tend to play in smaller, less elaborate venues, often competing in smaller cities. This term is used in North America with regard to several organizations competing in various sports. They generally have lesser fan bases and smaller budgets.
The minor league concept is a manifestation of the franchise system used in North American sports, whereby the group of major league teams in each sport is fixed for long periods between expansions or other adjustments, which only take place with the consent of the major league owners. In other parts of the world there is usually either a system of annual promotion and relegation, meaning that clubs have no fixed status in the hierarchy, or there is only one professional league per country in each sport, rendering the major/minor distinction irrelevant.
The most famous minor league organization is in baseball. Minor league baseball is almost as old as the professional game itself, and at first consisted of attempts to play baseball in smaller cities and towns independent of the National League, the first true major baseball league. Soon, scouts for the National League were travelling to watch minor league teams play and attempting to sign the more talented ones away. Some sports historians cite the connection between the other major league, the American League and its minor league forebear, the Western Association. Soon Major League Baseball began formal developmental agreements with some minor league teams, while others remained independent. The most prominent independent minor baseball league today is probably the Northern League.
Baseball is not the only sport with minor leagues. In fact all of the prominent team sports in North America have them. The sport with the next most extensive system of minor leagues other than baseball is ice hockey. The American Hockey League is the most prominent of these, with most NHL teams having a "farm" team in the AHL where they develop young players and occasionally rehabilitate older players who are injured or whose quality of play has slumped. These teams in turn have lower-level minor leagues to draw players from and pass players down to. Junior and Senior hockey leagues are similar, but not exactly equivalent, to minor leagues due to their age and experience restrictions.
The National Basketball Association has an affiliated minor league, the NBA Development League (also called the "D-League"). Additionally, the Continental Basketball Association has served some of the purposes of a minor league for the NBA for many years. However, there are no direct developmental agreements between CBA and NBA teams the way that there are between Major League Baseball and National Hockey League teams and their minor league affiliates.
While there are various semi-professional American football leagues, none have any affiliation with the National Football League. Its only "official" developmental minor league is NFL Europa. Many consider the Arena Football League to be a minor league, but this is not exactly the case. Arena Football is played under very different conditions, and the AFL has survived for 20 years and has now established itself as a viable professional league. The AFL has its own minor league, af2, and several independent leagues that play a similar game exist.
Other sports organizations considered to be minor leagues are the golf Nationwide Tour, affiliated with the PGA Tour, NASCAR's Busch Series and Craftsman Truck Series, and various other affiliated satellite tours of other individual sports.