 The final series to determine its champion has been called the "World Series" (originally "World's Championship Series" and then "World's Series") as far back as the National League's contests with the American Association during the 1880s.All of the 16 domestic Minor League Baseball leagues which are affiliated with Major League Baseball conduct playoffs after their regular season to determine champions.Most leagues at the Triple-A, Double-A, and Class A Advanced classification levels include four qualifying teams which compete in two best-of-five rounds