One hundred and 10 years ago, the Chicago Cubs ended the regular season with a 116-36 record. That .763 winning percentage is the best in modern baseball history by a comfortable margin, but the Cubs went on to drop the World Series to the White Sox in six games. Might they still be the greatest team in baseball history?
We recently calculated historical Elo ratings for every team after every game as part of our Complete History Of MLB interactive graphic. (We've done the same for the NBA and NFL.) Elo ratings are one of our preferred metrics at FiveThirtyEight, because their simple inputs make them useful for comparing the relative strengths of teams across the entire history of a league. We can also use Elo to calculate season ratings for every MLB team since 1903, when the first modern World Series was played.1 We arrived at an overall season rating - what the table below calls "composite" Elo - by blending each team's peak, average and final Elo for each season. This lets us take into account a team's highest level of performance, its sustained performance throughout the season and, broadly, how well it did in the postseason.2
More Sports So who comes out on top? The 1906 Cubs have the highest peak Elo, but because of their World Series loss, they rate as the second-best team since 1903, behind the 1939 New York Yankees. We ranked all 2,374 team-seasons from 1903 to 2015.