1. In 1777, the Battle of Brandywine took place near Chadds Ford, Pennsylvania. The battle involved British and American troops, and although the British ultimately won, it gave the American forces confidence and helped them prevent the British from capturing Philadelphia.

2. On September 15, 1787, Delaware became the first state to ratify the United States Constitution. This important event is celebrated each year as Constitution Day.

3. The Delaware River and Bay Authority was established on September 15, 1961. The authority is responsible for maintaining and operating a number of transportation facilities in the Delaware River and Bay region.

4. On September 15, 1972, Hurricane Agnes struck the East Coast, causing widespread flooding in Delaware and other states. The storm caused significant damage to homes and businesses and resulted in several fatalities.

5. In 2009, President Barack Obama delivered a speech at the University of Delaware in Newark, Delaware. The speech focused on the importance of clean energy and sustainable practices, and was seen by many as a key moment in the development of national energy policy.