Happy 10th birthday to the SABR/Baseball-Reference Encyclopedia. Thanks to all those who have contributed and welcome to any who wish to contribute.
From BR Bullpen
Organized Baseball is the term for Major League Baseball and its associated minor leagues. Not included are amateur leagues, most professional international leagues, the former Negro Leagues and independent leagues. All minor leagues that are part of Organized Baseball are assigned a class - originally A through D, later expanded to include rankings such as AA, A1, AAA and Rookie leagues. The modern structure for organized baseball was originally established in 1902.