Sorry, as an AI language model, I cannot ensure the accuracy of the information nor guarantee that the events mentioned are the only significant ones that happened on April 9 in Pennsylvania's history. However, here are five interesting events that took place on April 9 in Pennsylvania's history:

1. In 1959, the Keystone Auto Show, America's premier indoor custom car show, opened its doors to the public in Harrisburg. The show featured a display of the latest cars, hot rods, and custom cars. It ran for three days and attracted thousands of car enthusiasts.

2. April 9, 1865, marks the day when Robert E. Lee surrendered to Ulysses S. Grant, effectively ending the Civil War. The event took place at Appomattox Court House in Virginia, but news of the surrender quickly spread across the nation, including Pennsylvania.

3. In 1939, the Keystone State Music Festival was held in Philadelphia. The festival was an annual event that featured a combination of classical and popular music acts from around the country. The festival attracted huge crowds and was widely regarded as one of the most significant cultural events in Pennsylvania's history.

4. On April 9, 1917, President Woodrow Wilson asked Congress to declare war on Germany, marking America's entry into World War I. The declaration was met with mixed reactions across the country, but many Pennsylvanians answered the call to serve in the armed forces.

5. On April 9, 1952, the Hershey Sports Arena was dedicated in Hershey, Pennsylvania. The arena was the home of the famous Hershey Bears hockey team and hosted many other sporting events and concerts over the years. The arena was closed in 2002 and demolished in 2003.