The “Official Baseball Rules” govern all professional play in the United States and Canada, including the World Baseball Classic. The complete rules are published as the Official Baseball Rules at MLB.com, the official web site of Major League Baseball in the United States and Canada. The rules are also published in book form in North America by the Sporting News. Many amateur and youth leagues use the “OBR” with only a few modifications for safety.
Other slightly modified versions of the “Official Baseball Rules” are used in competitions operated by the International Baseball Federation (IBAF), including the Olympics and the World Cup, most leagues outside North America (such as Japan’s Nippon Professional Baseball), and youth baseball organizations such as Little League, PONY League, and Cal Ripken League.
The baseball rulebook of the NCAA, aside from governing the games of that organization’s members, is also utilized by several other competitions involving college-aged players.
U.S. high school and high school-age baseball is governed by the rules of the National Federation of State High School Associations (NFHS).
The history of baseball in the United States can be traced to the 18th century, when amateurs played a baseball-like game by their own informal rules using improvised equipment. The popularity of the sport inspired the semipro national baseball clubs in the 1860s.