1. In 1788, the Commonwealth of Pennsylvania became the second state to ratify the U.S. Constitution, after Delaware. This secured Pennsylvania's place in the newly formed United States of America and helped establish a strong federal government.

2. On May 23, 1904, the first Pennsylvania motor vehicle registration plates were issued. The plate was made of aluminum and featured the state's coat of arms, with the words "Pennsylvania" and "Automobile" printed on either side. The plates were required for all vehicles in the state and cost $1 each.

3. The Johnstown Flood occurred on May 31, 1889, but the heavy rains that caused the disaster began on May 23. Close to 2,200 people lost their lives in the flood, which is still considered one of the deadliest natural disasters in U.S. history. The flood prompted wide-ranging changes in flood control and disaster relief efforts across the country.

4. On May 23, 1611, colonist Thomas Dale established the first permanent English settlement in what is now Chester, Pennsylvania. The settlement, known as New Bermuda, was meant to serve as a base for trade and exploration in the region. However, conflicts with the local Lenape people led to the settlement's decline and eventual abandonment.

5. Pennsylvania played a crucial role in the American Revolutionary War, and May 23 saw several key events related to the conflict. In 1777, British General William Howe occupied Philadelphia, which served as the capital of the fledgling United States at the time. And on May 23, 1780, the Battle of Connecticut Farms was fought in New Jersey, a crucial engagement in the wider campaign for independence that saw Pennsylvania militiamen fighting alongside their fellow patriots.