1. On September 17, 1787, Connecticut was one of the first states to ratify the United States Constitution. Connecticut played a significant role in the creation and ratification of the Constitution, with its delegates playing an active role in the drafting of the document.

2. In 1862, the Battle of Antietam took place, marking the bloodiest single-day battle in United States history. Connecticut soldiers fought in the battle, with many losing their lives or being wounded in the conflict.

3. On September 17, 1939, the Connecticut State Library and Supreme Court building was officially dedicated. The building was designed by famed architect Egerton Swartwout and is considered a masterpiece of Art Deco architecture.

4. In 1987, Connecticut's Foxwoods Resort Casino opened its doors, becoming one of the largest casinos in the world. The casino has helped to boost the local economy and has become a major tourist attraction.

5. On September 17, 2009, a gas explosion occurred in downtown Middletown, Connecticut, killing six people and injuring several others. The explosion was caused by a natural gas leak and resulted in significant damage to nearby buildings. The tragedy served as a reminder of the importance of proper gas line maintenance and safety precautions.