1. In 1777, the Battle of Germantown took place in Pennsylvania during the American Revolutionary War. This battle was fought between the British Army and the Continental Army, led by General George Washington. Although the Americans suffered a defeat, they were able to inflict significant damage on the British Army.

2. In 1890, the first World Series in baseball history was played between the National League champion Brooklyn Bridegrooms and the American Association champion Louisville Colonels. The series lasted 7 games and was won by the Bridegrooms.

3. In 1919, the Pittsburgh Pirates won the World Series in baseball. The Pirates defeated the Chicago White Sox in the series, which was later marred by the Black Sox scandal, in which several White Sox players were accused of throwing games.

4. In 1963, Congress passed the Clean Air Act, which was designed to regulate air pollution in the United States. The act has been amended several times since its passage and is considered to be one of the most important environmental laws in U.S. history.

5. In 1975, the Philadelphia Flyers and the Pittsburgh Penguins played the first ever game at the Spectrum, which was a new arena in Philadelphia. The Flyers won the game 4-1 and went on to win their second consecutive Stanley Cup that season.