1. The Treaty of Hartford was signed on December 3, 1638, between the English colonists and the Pequot tribe, ending the Pequot War. The agreement gave the colonists control of Pequot lands and required the Pequot to pay an annual tribute.

2. Connecticut's first constitution was adopted on December 3, 1818. The document established the state's three branches of government, including a governor, legislature, and judicial system.

3. On December 3, 1833, the Hartford and New Haven Railroad began service, becoming the first steam-powered railroad in Connecticut. The line initially ran between Hartford and New Haven and helped stimulate economic growth and transport goods and people throughout the state.

4. December 3, 1887, marks the birth of Joseph W. Alsop, a prominent newspaper columnist and political commentator. Alsop's commentary spanned over four decades, and he became known for his insight into world politics and his close connections with government officials.

5. Bridgeport-born physician and astronaut Bernard A. Harris, Jr. became the first African American to walk in space on December 3, 1995, during the second US-Russian joint space mission. Harris completed two space missions and conducted research into the human cardiovascular system during his time in orbit.