Bill,
I am surprised. If you had put this up as a question, I would have guessed either National League August/September 1965, where the Pirates, Giants and Dodgers went toe to toe for about two months, or American League East September 1974, with the Orioles and Yankees. The Yankees were eliminated on the next to last game of the season; Doc Medich then threw a no hitter in the final game.
Big Hitter