1. On August 3, 1777, British troops under General William Howe landed at Head of Elk, Maryland, now called Elkton, to launch an attack on Philadelphia during the American Revolutionary War. This marked the beginning of the Philadelphia campaign, which would lead to the Battle of Brandywine and eventually the capture of Philadelphia by the British.

2. August 3, 1863, marked the final day of the Battle of Gettysburg during the American Civil War. Although the battle had ended on July 4, Confederate General Robert E. Lee's army retreated across the Potomac River into Virginia on August 3, effectively ending the invasion of the North and marking a turning point in the war.

3. Delaware became the first state to ratify the United States Constitution on December 7, 1787, but the state's constitution was not actually approved until August 3, 1792. This constitution created a bicameral legislature and established the Office of the Governor, which was previously known as the President of Delaware.

4. On August 3, 1907, the DuPont Company built the first reinforced plastic airplane, known as the DuPont Model-A, which was flown by Eugene Ely in Hammondsport, New York. This marked an important milestone in aviation history, as the use of reinforced plastics allowed for lighter and stronger aircraft.

5. August 3, 1967, marked the opening of the I-95 Delaware Memorial Bridge, which spans the Delaware River and connects Delaware and New Jersey. This bridge is a major transportation artery on the east coast, carrying millions of vehicles each year and serving as a vital link between Philadelphia and Washington, D.C.