1. The Battle of Brandywine: On September 15, 1777, the Battle of Brandywine took place in Chester County during the American Revolutionary War. The British army, under the command of General William Howe, defeated the Continental Army, led by General George Washington.

2. Pennsylvania Constitution: The Pennsylvania Constitution was adopted on September 15, 1790. The constitution established Pennsylvania as a self-governed commonwealth with a bicameral legislature and a governor elected by the people.

3. Liberty Bell Arrival: On September 15, 1784, the Liberty Bell arrived in Philadelphia after being transported from England. Today, the Liberty Bell is an iconic symbol of American independence and is housed in the Independence National Historical Park.

4. Hershey Park: Hershey Park, originally called Hershey Park Amusement Resort, opened on September 15, 1907, in Hershey, Pennsylvania. The park was created by Milton Hershey, the founder of the Hershey's chocolate company, as a recreational spot for his factory workers.

5. Hurricane Ivan: Hurricane Ivan made landfall on the coast of Alabama on September 15, 2004, causing widespread destruction and flooding. Pennsylvania was one of several states that provided assistance to the affected areas, including sending emergency responders and supplies.