History of the Day for:
- 1848: Niagara Falls stopped flowing for 30 hours because of an ice jam blocking the Niagara River.
- 1882: The Knights of Columbus organization was granted a charter by the State of Connecticut.
- 1932: Comedian Jack Benny appeared on radio for the first time.
- 1941: World War II: British Royal Navy and Royal Australian Navy forces defeat those of the Italian Regia Marina off the Peloponnesus coast of Greece in the Battle of Cape Matapan.
- 1942: The Bombing of Lübeck in World War II is the first major success for the RAF Bomber Command against Germany and a German city.
- 1945: World War II: Last day of V-1 flying bomb attacks on England.
- 1951: Ethel and Julius Rosenberg are convicted of conspiracy to commit espionage.
- 1951: Julius and Ethel Rosenberg were convicted of spying; Rodgers and Hammerstein's musical "The King and I" opened on Broadway.
- 1962: Jack Paar hosted NBC's "Tonight" show for the final time.
- 1967: The first nationwide strike in the 30-year history of the American Federation of Television and Radio Artists began.
- 1971: Army Lieutenant William L. Calley Jr. was convicted of murdering at least 22 Vietnamese civilians in the My Lai massacre: a jury in Los Angeles recommended the death penalty for Charles Manson and three female followers for the 1969 Tate-La Bianca murders; the development of a serum hepatitis vaccine for children was announced.
- 1973: The last U.S. troops left South Vietnam, ending America's direct military involvement in the Vietnam War.
- 1974: Eight Ohio National Guardsmen were indicted on charges stemming from the shooting deaths of four students at Kent State University.
- 1993: "Unforgiven" won the Academy Award for best picture as well as best director for Clint Eastwood; Emma Thompson won best actress for "Howards End" and Al Pacino won best actor for "Scent of a Woman."
- 1999: The Dow Jones Industrial Average closes above the 10,000 mark (10,006.78) for the first time ever, during the height of the internet boom.
- 2004: Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia and Slovenia join NATO as full members.
- 2004: The Republic of Ireland becomes the first country in the world to ban smoking in all work places, including bars and restaurants.
- 2008: 35 Countries & over 370 cities join Earth Hour for the first time.