1. On July 17, 1818, the first steamboat to navigate the Connecticut River, the William IV, made its first voyage from Hartford to Saybrook. This marked a significant advancement in transportation in the state.

2. The state of Connecticut officially abolished slavery on July 17, 1848, becoming the last state in New England to do so. However, the abolition was only gradual and did not fully take effect until 1854.

3. On July 17, 1878, the first telephone exchange in the state was established in New Haven. It had 28 subscribers, including Yale University and the New Haven Register.

4. On this day in 1955, the first nuclear-powered submarine, the USS Nautilus, returned to its homeport in Groton after completing its historic underwater journey from the Atlantic to the Pacific via the North Pole.

5. Notable Connecticut-born inventor and innovator Samuel Colt was born on July 17, 1814. He is best known for his development of the revolver and for founding the Colt Patent Firearms Manufacturing Company in Hartford, which helped to establish the city as an important center for the gun industry.