1. On April 4, 1792, the Pennsylvania Legislature passed an act creating the city of Pittsburgh. The city was named after Sir William Pitt, the British Prime Minister who supported the colonists during the American Revolution.

2. On April 4, 1865, General Robert E. Lee and his Confederate Army began their retreat from Richmond, Virginia, heading west to join forces with General Joseph E. Johnston's army in North Carolina. The retreat would ultimately lead to the end of the Civil War.

3. On April 4, 1938, the longest recorded tornado track in Pennsylvania history occurred. The tornado traveled 106 miles through five counties, causing extensive damage and killing at least two people.

4. On April 4, 1949, a massive train wreck occurred in Shohola, Pennsylvania, when two passenger trains collided on a single-track line. The crash killed 45 people and injured more than 100 others in what is considered one of the worst train disasters in U.S. history.

5. On April 4, 1968, civil rights leader Martin Luther King Jr. was assassinated in Memphis, Tennessee. King had previously given a famous speech in Pennsylvania when he addressed a crowd of 30,000 people at the Freedom Rally in Philadelphia on August 3, 1965.