1. In 1788, Pennsylvania became the second state to ratify the United States Constitution, after Delaware. The state played a critical role in the formation and early history of the nation, hosting both the First and Second Continental Congresses in Philadelphia.

2. On June 25, 1876, the Battle of Little Bighorn took place in present-day Montana. Although not in Pennsylvania, the battle is tied to the state as one of the commanding officers was General George Armstrong Custer, who was born in New Rumley, Ohio, near the Pennsylvania border.

3. In 1892, the Homestead Strike began at the Carnegie Steel Company in Homestead, Pennsylvania. The labor dispute, which lasted for several months, saw workers clash with company officials and Pinkerton detectives hired to quell the strike.

4. On June 25, 1917, the East St. Clair Township mine explosion occurred in Westmoreland County, killing over 100 men. The disaster brought attention to the dangerous working conditions faced by coal miners in the state and sparked efforts to improve mine safety.

5. In 1979, the Susquehanna River flooded, causing widespread damage throughout the state. The disaster led to changes in flood control and warning systems to better protect Pennsylvania communities from future floods.