The World Series is played between the champion clubs of the American League and the National League, which collectively include 29 clubs based in the United States and one club from Canada. The “modern” World Series has been an annual event since 1903. Baseball has employed various championship formulas since the 1860s. When the term “World Series” is used by itself, it is usually understood to refer to the “modern” World Series exclusively.

The World Series championship is determined through a best-of-seven playoff. Best-of-seven has been the format of all the modern World Series except in 1903, 1919, 1920 and 1921 when the winner was determined through a best-of-nine playoff. The Series winner is awarded the World Series Trophy, as well as individual World Series rings. The Series winner also receives a larger proportion of the gate receipts than does the Series loser.

The New York Yankees, of the American League, have played in 39 of the 104 Series through 2008 and have won 26 World Series championships, the most of any Major League franchise. For the National League, the Dodgers have appeared in the Series the most at 18 times (9 each in Brooklyn and Los Angeles), but have won the Series only 6 times (once as Brooklyn, five times as Los Angeles). The St. Louis Cardinals have represented the National League 17 times and have won 10 championships, which is the most for any National League team.[1] The Chicago Cubs have the longest streak of not winning the World Series, with their last championship coming in 1908. [Wikipedia]