• 240 BC - 1st recorded perihelion passage of Halley's Comet.
• 1282 - The people of Sicily rebel against the Angevin king Charles I, in what becomes known as the Sicilian Vespers.
• 1296 - Edward I sacks Berwick-upon-Tweed, during armed conflict between Scotland and England.
• 1814 - Napoleonic Wars: Sixth Coalition forces march into Paris.
• 1814 - Murat issues the Rimini Declaration which would later inspire Italian Unification.
• 1822 - Florida Territory created in the United States.
• 1842 - Anesthesia is used for the first time in an operation by Dr. Crawford Long.
• 1844 - One of the most important battles of the Dominican War of Independence from Haiti takes place near the city of Santiago de los Caballeros.
• 1855 - Origins of the American Civil War: Bleeding Kansas - "Border Ruffians" from Missouri invade Kansas and force election of a pro-slavery legislature.
• 1856 - The Treaty of Paris (1856) is signed, ending the Crimean War.
• 1858 - Hymen Lipman patents a pencil with an attached eraser.
• 1863 - Danish prince Wilhelm Georg is chosen as King George of Greece.
• 1867 - Alaska is purchased for $7.2 million, about 2 cent/acre ($4.19/km²), by United States Secretary of State William H. Seward. The news media call this Seward's Folly.
• 1870 - Texas is readmitted to the Union following Reconstruction.
• 1885 - The Battle for Kushka triggers the Pandjeh Incident which nearly gives rise to war between the British Empire and Russian Empire.
• 1909 - The Queensboro Bridge opens, linking Manhattan & Queens.
• 1910 - Mississippi Legislature founded The University of Southern Mississippi.
• 1912 - Sultan Abdelhafid signs the Treaty of Fez, making Morocco a French protectorate.
• 1939 - The Heinkel He 100 fighter sets the world airspeed record of 463 mph.
• 1939 - First flight of the Australian C.A.C. CA-16 Wirraway.
• 1940 - Sino-Japanese War: Japan declares Nanking to be the capital of a new Chinese puppet government, nominally controlled by Wang Ching-wei.
• 1945 - World War II: Soviet Union forces invade Austria and take Vienna, Polish and Soviet forces liberate Gdańsk.
• 1945 - World War II: a defecting German pilot delivers a Messerschmitt Me 262A-1 to Americans.
• 1949 - Riot breaks out in Austurvöllur square in Reykjavík, when Iceland joined NATO.
• 1951 - Remington Rand delivers the first UNIVAC I computer to the United States Census Bureau.
• 1954 - Yonge Street subway line opens in Toronto. It is the first subway in Canada.
• 1961 - The Single Convention on Narcotic Drugs is signed at New York.
• 1965 - Vietnam War: A car bomb explodes in front of the U.S. Embassy in Saigon, killing 22 and wounding 183 others.
• 1972 - Vietnam War: The Easter Offensive begins after North Vietnamese forces cross into the Demilitarized Zone (DMZ) of South Vietnam.
• 1979 - Airey Neave, a British politician, is killed by a car bomb as he exits the Palace of Westminster. The Irish National Liberation Army claims responsibility.
• 1981 - President Ronald Reagan is shot in the chest outside a Washington, D.C., hotel by John Hinckley, Jr.
• 1982 - Space Shuttle program: STS-3 Mission completed with the landing of Columbia at White Sands Missile Range, New Mexico.
• 1997 - Five (channel) Begins broadcasting in the UK
• 2006 - Marcos Pontes is the first Brazilian astronaut in space.
• 2006 - UK Terrorism Act 2006 becomes law.

Births