1. In 1752, Benjamin Franklin conducted a famous experiment in Philadelphia involving electricity and a kite. He flew the kite in a thunderstorm and proved that lightning was a form of electricity. This groundbreaking discovery led to the development of modern lightning rods.

2. On June 15, 1775, the Continental Congress appointed George Washington as Commander-in-Chief of the Continental Army. Washington would go on to lead the army to victory in the Revolutionary War and become the first President of the United States.

3. The Pennsylvania Railroad, one of the largest and most influential railway companies in American history, was incorporated on June 15, 1846. The railroad helped to expand westward settlement, connect the country's industries and resources, and spur economic growth and development.

4. The National Constitution Center, an interactive museum and educational facility dedicated to the United States Constitution, opened its doors in Philadelphia on June 15, 2003. The Center boasts exhibits, historical artifacts, and educational programs that explore the history, formation, and significance of the Constitution.

5. On June 15, 2012, Pennsylvania became the 24th state to legalize medical marijuana when Governor Tom Corbett signed the Compassionate Use of Medical Cannabis Act into law. The law allowed for the use of marijuana for treating certain medical conditions, such as epilepsy, multiple sclerosis, and cancer, and provided guidelines for its sale, distribution, and usage.