1. Delaware ratifies the United States Constitution - On June 30, 1787, the state of Delaware became the first to ratify the United States Constitution. This was a significant moment in American history as it paved the way for the formation of the federal government and the establishment of the United States as a nation.

2. The Zwaanendael Museum opens - June 30, 1931, marked the opening of the Zwaanendael Museum in Lewes, Delaware. The museum is named after the Zwaanendael Colony, a short-lived Dutch settlement established in the area in 1631. The museum showcases Delaware's early history and features exhibits on the Zwaanendael Colony, the early days of Lewes, and the maritime history of the region.

3. The USS Delaware is launched - June 30, 1910, saw the launch of the USS Delaware, a battleship that served in both World War I and II. The ship was commissioned on April 4, 1910, and was the lead ship of its class. The USS Delaware participated in several important naval battles during World War II, including the Battle of Surigao Strait, the largest naval battle of the war.

4. Delaware State Police is formed - On June 30, 1923, the Delaware State Police was officially formed. The agency was created to provide statewide law enforcement services and to assist local police departments in the state. Today, the Delaware State Police is responsible for maintaining public safety and enforcing the law throughout Delaware.

5. First commercially successful nylon production - June 30, 1940, marked the first commercially successful production of nylon, a synthetic polymer fiber. The production took place at the DuPont Experimental Station in Wilmington, Delaware. Nylon went on to become a widely used material in a variety of industries, including clothing, carpeting, and packaging.