1. On June 23, 1637, a battle took place in present-day Fairfield County between the Pequot tribe and English colonists. The conflict, known as the Pequot War, resulted in the deaths of over 400 Pequot people and marked a turning point in the colonization of Connecticut.

2. On June 23, 1818, Connecticut became the 5th state to ratify the Constitution's 20th Amendment. This amendment established the terms of the President and Vice President and was part of a series of amendments known as the Bill of Rights.

3. On June 23, 1875, the Connecticut Agricultural Experiment Station was established in New Haven. This institution was the first of its kind in the United States and was created to promote agricultural research and education.

4. On June 23, 1906, the Charter Oak monument was dedicated in Hartford's Bushnell Park. The monument commemorates a famous story in Connecticut history where colonists hid the government's charter in a hollow oak tree during a power struggle with the British in 1687.

5. On June 23, 2005, Connecticut became the first state to pass a law legalizing same-sex civil unions. While not full marriage equality, the law granted all of the legal rights and responsibilities of marriage to same-sex couples. This was a landmark moment in the fight for LGBTQ+ rights in the United States.