In 1903 the first World Series was held, evolving today to a Wild Card Series and Division Series never before seen in the history of the Majors.
Two teams will be seated per league (Dodgers-Atlanta, Houston-Yankees), awaiting the outcome of the first best-of-three Wild Card Series at the home of the division winners with the worst record this season, the Cardinals and Guardians. The Mets and Toronto will also have the home advantage for being the two ninth-best records of the six that advanced via Wild Card (plus San Diego and Phillies in the NL; Seattle and Tampa in the AL).
To get to what baseball is today we must go to the genesis. In 1903 there were no divisions, only league champions and 16 teams. The American was made up of the Boston American, then Red Sox, Athletics, Cleveland, Yankees, Detroit, St. Louis Browns and Washington. The Old Circuit was made up of Pittsburgh, Cardinals, Phillies, Chicago, Boston, Cincinnati, NY Giants and Brooklyn Dodgers. Boston won the crown by beating Pittsburgh.
In 1958 a considerable change was made, moving the teams to an area as far away as California. The Dodgers wanted the construction of a new stadium, denying such request the city of New York. The Angels, who were after the fading Senators franchise, landed both the Dodgers and the Giants, taking their rivalry all the way to the Wild West.
In 1961, the first expansion of the Majors took place, adding the Minnesota Twins and the Angels to the American League. The following year the Houston Colts and the New York Metros joined the National.
The first great revolution in baseball was implemented in 1969: the Championship Series. Four teams joined (Oakland Athletics and Seattle Pilots in the AL; San Diego Padres and Montreal Expos in the National, totaling 24 teams), breaking the outdated mold of one winner in each league.
The Seattle Mariners and Toronto Blue Jays debuted in 1977, reaching 26 teams; 14 in the American, 12 in the National. In 1993 the Marlins and the Rockies entered.