In recent years the Jets and Giants have been so bad that I have developed a morbid fascination as to whether they would surpass the worst combined record in New York professional football history, surpassing 1976 when both teams went 3-11 (.211). Year after year they have come close, but not quite pulled it off.
But this year the Mets and Yankees are so good, with a .644 winning percentage before last night, that I have begun to wonder if this could be the best year in New York professional baseball history.
So I downloaded all the records of all the teams from Baseball Reference for all the years, and lined them up in a spreadsheet. Not just the Mets and Yankees, or even the Giants and Dodgers and all the names the Dodgers were previously called, but all the other defunct franchises, including those in the Negro Leagues. This is what I found.
The highest winning percentage in New York professional baseball history was 1961 at .672. But like Roger Maris' home run record that year it gets an asterisk, since the Yankees were the only team in town that year, and on a mission after losing a World Series they had dominated in 1960. Going back the the 1870s, there only six years when New York City had only one team. And one of those years, 1876, featured the worst year in New York baseball history, with the New York Mutuals posting a .377 winning percentage. And then folding, leaving New York with no teams until 1883.
The best combined record for two or more teams in New York City was 1889, when the New York Giants and Brooklyn Bridegrooms (later the Dodgers) posted a .664 winning percentage. That got people so excited that in 1890 these teams were joined by the Brooklyn Gladiators, the Brooklyn Ward's Wonders, and a different New York Giants of the Player's League. None of these teams lasted more than one year.
The highest combined winning percentage for the Yankees and Mets was 1998, when the Yankees won the most games of their 1990s dynasty at 114 and the Mets also had a good team with 88 wins. The combined winning percentage was .623. The second highest combined winning percentage for these teams was 1986, when the Mets won the most games of their 1980s dynasty at 108, and the Yankees also had a good team with 90 wins. The combined winning percentage was .611. The worst combined winning percentage for these teams was .393 in 1965, when the expansion Mets still stunk and the Yankees dynasty had collapsed.
How about the "Golden Age" of 1947 to 1957, when New York dominated baseball and just about everything else? The best combined winning percentages were .632 in 1954 and .626 in 1951. The Yankees and Dodgers had great records every year of this era, but in these two years the Giants were also great and went to the World Series, winning it in 1954.
In summary, at their current pace the Mets and Yankees would have the best combined record for the two teams in history by a comfortable margin, and also surpass the best combined record of the Yankees, Giants and Dodgers in the "Golden Age." They trail only the one-team record of the Yankees in 1961, the year before the Mets started play, and the two-team record of 1889, before the Yankees existed.