1478 - Pazzi conspirators attacked Lorenzo and killed Giuliano de'Medici.
1514 - Copernicus made his first observations of Saturn.
1607 - The British established an American colony at Cape Henry, Virginia. It was the first permanent English establishment in the Western Hemisphere.
1819 - The first Odd Fellows lodge in the U.S. was established in Baltimore, MD.
1865 - Joseph E. Johnston surrendered the Army of Tennessee to Sherman during the American Civil War.
1865 - John Wilkes Booth was killed by the U.S. Federal Cavalry.
1906 - In Hawaii, motion pictures were shown for the first time.
1921 - Weather broadcasts were heard for the first time on radio in St. Louis, MO.
1929 - First non-stop flight from England to India was completed.
1931 - New York Yankee Lou Gehrig hit a home run but was called out for passing a runner.
1931 - NBC premiered "Lum and Abner." It was on the air for 24 years.
1937 - German planes attacked Guernica, Spain, during the Spanish Civil War for the Spanish nationalist government. This raid is considered one of the first to be attacks on a civilian population by a modern air force.
1937 - "LIFE" magazine was printed without the word "LIFE" on the cover.
1937 - "Lorenzo Jones" premiered on NBC radio.
1941 - An organ was played at a baseball stadium for the first time in Chicago, IL.
1945 - Marshal Henri Philippe Petain, the head of France's Vichy government during World War II, was arrested.
1952 - Patty Berg set a new record for major women’s golf competition when she shot a 64 over 18 holes in a tournament in Richmond, CA.
1954 - Grace Kelly was on the cover of "LIFE" magazine.
1964 - The African nations of Tanganyika and Zanzibar merged to form Tanzania.
1964 - The Boston Celtics won their sixth consecutive NBA title. They won two more before the streak came to an end.
1968 - Students seized the administration building at Ohio State University.
1982 - The British announced that Argentina had surrendered on South Georgia.
1983 - Dow Jones Industrial Average broke 1,200 for first time.
1985 - In Argentina, a fire at a mental hospital killed 79 people and injured 247.
1986 - The world’s worst nuclear disaster to date occurred at Chernobyl, in Kiev. Thirty-one people died in the incident and thousands more were exposed to radioactive material.
1998 - Auxiliary Bishop Juan Gerardi Conedera was bludgeoned to death two days after a report he'd compiled on atrocities during Guatemala's 36-year civil war was made public.
2000 - Charles Wang and Sanjay Kumar purchased the NHL's New York Islanders.
2002 - In Erfurt, Germany, an expelled student killed 17 people at his former school. The student then killed himself.