1. On May 20, 1846, the Amistad captives were released from the jail in New Haven after two years of imprisonment. The African captives had been illegally brought to the United States on a slave ship, but seized control of the ship and were subsequently arrested and put on trial. Their case eventually made its way to the Supreme Court, which ruled in their favor and allowed them to return to their homeland.

2. On May 20, 1774, delegates from Connecticut attended the First Continental Congress in Philadelphia. The congress was called in response to the Coercive Acts, which were passed by the British Parliament in response to the Boston Tea Party. The delegates from Connecticut were among those who voted to endorse a boycott of British goods.

3. On May 20, 1927, aviator Charles Lindbergh flew his plane, the Spirit of St. Louis, over Connecticut on his way to New York City. Lindbergh had just completed the first solo non-stop transatlantic flight from New York to Paris, and his triumphant return to the United States was celebrated with ticker-tape parades in New York and other cities.

4. On May 20, 1970, student protesters at Yale University burned down the ROTC building on campus in protest of the Vietnam War. The incident was part of a nationwide wave of protests against the war, and marked a turning point for many college campuses as the conflict entered its later stages.

5. On May 20, 1818, the first volume of the first American encyclopedia, the American Cyclopaedia, was published by the firm of Carey and Lea in Philadelphia. The encyclopedia was edited by Francis Lieber, a German immigrant and political philosopher who had come to the United States after participating in the failed liberal uprising of 1848. The encyclopedia was an important early example of American scholarship and innovation, and set a high standard for subsequent encyclopedias and reference works.