1. On September 2, 1752, the Penn family signed the famous Treaty of Shackamaxon with the Lenape Native Americans, securing peaceful relations between the two groups. This treaty is considered a significant moment in Pennsylvania's colonial history.

2. In 1823, Allegheny County's first courthouse was completed on September 2. The courthouse would serve as a hub for legal proceedings and public offices in Pittsburgh for over 50 years before being replaced by a newer building.

3. On September 2, 1915, a massive explosion tore through the Dupont Powder Mill in Fontanet, killing over 50 people and injuring many more. The tragedy was one of the deadliest industrial accidents in Pennsylvania history.

4. In 1936, the Allegheny County Airport, now known as Pittsburgh International Airport, opened to the public on September 2. The airport has since become one of the busiest in the country, serving millions of passengers each year.

5. Finally, on September 2, 1945, the United States signed the Japanese Instrument of Surrender, formally ending World War II. The war had a profound impact on Pennsylvania and the nation as a whole, and the signing of the surrender marked a transition into a new era of peace and rebuilding.