1. In 1865, the assassination of President Abraham Lincoln's assassin, John Wilkes Booth, took place in Virginia. Booth had recently fled to a farm in Maryland, where Union soldiers had tracked him and cornered him in a barn. After refusing to surrender, Booth was shot and killed.

2. In 1898, the USS Indiana was launched from Philadelphia. The Indiana was one of only four battleships in the US Navy at the time and was part of the reason for America's entrance into the Spanish-American War.

3. In 1964, a major tornado outbreak occurred across the Eastern United States. Pennsylvania was one of the states hit by this outbreak, with several tornadoes touching down and causing damage.

4. In 1986, a nuclear accident occurred at the Three Mile Island power plant near Harrisburg, Pennsylvania. The accident resulted in the release of radioactive gas and caused concerns about the safety of the nuclear power industry.

5. In 2015, the first trial of comedian Bill Cosby on charges of sexual assault began in Montgomery County, Pennsylvania. Cosby was accused of drugging and assaulting a woman in 2004. The trial resulted in a mistrial, but Cosby was retried and ultimately convicted of three counts of sexual assault in 2018.