Going back to the days before the Yankees existed, the city’s best season in the 1800s was 1889, when the American Association’s Brooklyn Bridegrooms (later the Dodgers) and the National League’s Giants had a combined winning percentage of .669. The Giants beat the Dodgers in an interleague championship that preceded today’s World Series.
Unfortunately the records are not complete. The statistics of many Negro leagues are now considered on par with the other major leagues, but the records are not complete enough for accurate inclusion. A great season came in 1947 when the New York Cubans with Minnie Miñoso and Luis Tiant Sr. won the Negro World Series by a winning percentage of .687 while the Yanks, Giants and Dodgers combined had a record .589. But this season’s average win ratio is dragged down by the New York Black Yankees, who were a staggering 12-43.
It’s difficult to keep a winning percentage high when multiple teams are involved. Fittingly, the very best New York baseball season, dating back to the Giants’ formation as the New York Gothams in 1883, technically took place in the four dark years after the Giants and Dodgers moved west, leaving the Yankees as the only game in the city. It was 1961, the Mets were a year from stumbling into existence, and the Yankees were posting a .673 win percentage as Roger Maris and Mickey Mantle battled to break Babe Ruth’s home run record. They put the icing on the cake by winning the World Series.