1. The first permanent English settlement in Pennsylvania was established on May 17, 1681, at Marcus Hook by Swedish trader Ole Swenson. This settlement was part of the New Sweden colony along the Delaware River that was eventually annexed by the Dutch.

2. On May 17, 1775, the Continental Congress issued the Proclamation of Rebellion, which declared that the American colonies were in a state of rebellion against Great Britain. This was a critical moment in the lead up to the American Revolution.

3. The Pennsylvania State Capitol building was dedicated on May 17, 1906, after 30 years of planning, designing, and construction. The Beaux-Arts style building features a dome inspired by St. Peter's Basilica in Rome and numerous works of art and sculpture.

4. On May 17, 1954, the Supreme Court of the United States handed down its landmark decision in Brown v. Board of Education, which declared that segregation in public schools was unconstitutional. This decision helped to end legal segregation in the United States.

5. The Hershey's chocolate factory in Hershey, Pennsylvania, began operations on May 17, 1905. This factory was established by Milton Hershey, who had earlier founded the Hershey Chocolate Company in 1894. Today, Hershey's is one of the most well-known chocolate brands in the world.