On September 29, 1933, the Washington Senators, managed by Joe Cronin, defeated Joe McCarthy's New York Yankees, 8-5 to clinch the American League pennant.
The win, Washington's 98th of the season, was officially credited to pitcher Earl Whitehill, who improved his record to 22-8 by going seven innings and allowing five runs on eight hits with six walks and two strikeouts. Jack Russell pitched the final two innings to record his 13th save of the season. The losing pitcher for the Yankees, Red Ruffing, pitched all nine innings despite allowing eight runs on 10 hits and two walks.
Offensively, Washington's offensive stars were left fielder Heinie Manush, who doubled, homered, and drove in three runs; and first baseman Joe Kuhel, who went 2-for-4 with a double and drove in two more runs.
On that same day, Germany's Nazi government decreed that mid-size family farms could not be inherited by any other person except for the youngest son, could not be divided among the family, and could not be owned by any "non-Aryan" people.
So yes, it's been a very long time since a D.C. team played meaningful October baseball. Now, it's happened again.