1. On June 15, 1752, Benjamin Franklin conducted his famous kite experiment in Philadelphia, which formed the basis for the discovery of electricity. Although this event did not occur in Delaware, it is a significant part of American history.

2. In 1802, Mordecai Hopkins, a Delaware politician, launched a petition to abolish slavery in the state. The movement ultimately failed, but it was one of the first anti-slavery campaigns in the United States.

3. June 15, 1938, marks the establishment of the Delaware State Maritime Museum, dedicated to preserving and promoting the state's maritime and naval history. The museum is located in the historic town of Lewes and features exhibits on Delaware's role in the American Revolution, the War of 1812, and other maritime events.

4. On June 15, 1960, federal court judge Caleb Wright ordered the desegregation of Delaware's public schools, making Delaware one of the first states to comply with the Supreme Court's landmark Brown v. Board of Education decision.

5. In 1983, the first official firefly festival was held in Millsboro, Delaware, to honor the state's official insect, the firefly. The festival has since become an annual event, attracting thousands of visitors to the area each summer to watch the fireflies light up the night sky.