Minor League Baseball (MiLB) is a professional baseball organization below Major League Baseball (MLB), constituted of teams affiliated with MLB teams. It was founded on September 5, 1901, in response to the growing dominance of the National League and American League, as the National Association of Professional Baseball Leagues (NAPBL or NA).
MiLB originated as simply the organization of lower tiers of professional baseball in the United States, consisting of teams that lacked the financial means to compete with the National League and later the American League. The association of minor leagues remained independent throughout the early 20th century, protected by agreements with the major leagues to ensure they were compensated when minor-league players were signed by major-league clubs. Later, MiLB evolved to be constituted entirely of affiliates of larger clubs, giving young prospects a chance to develop their skills before competing in the major leagues.