The World Series is a best-of-seven affair, so when the 2020 Fall Classic begins on Oct. 20, four wins will be required for a team to claim a championship.

But that has not always been the case. In fact, the event was born with a best-of-nine format. When the first World Series was played in 1903, it took the Boston Red Sox (then called the Americans) eight games to defeat the Pittsburgh Pirates, 5-3.

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When the World Series returned after a one-year hiatus in 1905, the next several were played as best-of-sevens. The best-of-nine format returned for three years from 1919-21, although none of those series actually went the full nine games.

Since 1922, the Fall Classic has always been a best-of-seven series. It has nearly always been played with a 2-3-2 format, meaning that one team gets home-field advantage in the first two games, as well as the last two (if necessary). The only exceptions were the 1943 and ‘45 World Series, which used a 3-4 format.

For most of that time, home-field advantage in the World Series alternated between the American League and the National League. That changed from 2003-16, when home field went to the league that won that year’s All-Star Game. Since 2017, that edge has gone to the World Series competitor with the better winning percentage in the regular season.

(In 2020, though, the team with home-field advantage won’t actually get to play at home, since the World Series will take place at a neutral site, Texas’ new ballpark, Globe Life Field. That team still will get to bat last in Games 1, 2, 6 and 7).

Of course, just because a series has a best-of-seven format, it doesn’t mean all seven games will be necessary. There have been 19 four-game sweeps in World Series history, while 28 have ended in five games, 24 have ended in six and 40 have gone seven (one of those a best-of-nine series). Meanwhile, four series also went to eight games -- three in the best-of-nine format and one, in 1912, when a tie extended the series.

These winner-take-all games are frequently classics. Of the 40 that have been played in best-of-seven World Series -- most recently the Nationals’ win over the Astros in 2019 -- more than half (22) have been decided by two runs or fewer. And road teams have played tough, going 21-19.