598 – Balkan Campaign: The Avars lift the siege at the Byzantine stronghold of Tomis. Their leader Bayan I retreats north of the Danube River after the Avaro-Slavic hordes are decimated by the plague.
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.
1815 – Joachim Murat issues the Rimini Proclamation which would later inspire Italian unification.
1818 – Physicist Augustin Fresnel reads a memoir on optical rotation to the French Academy of Sciences, reporting that when polarized light is "depolarized" by a Fresnel rhomb, its properties are preserved in any subsequent passage through an optically-rotating crystal or liquid.
1822 – The Florida Territory is created in the United States.
1841 – The National Bank of Greece is founded in Athens.
1842 – Ether anesthesia is used for the first time, in an operation by the American surgeon 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: "Border Ruffians" from Missouri invade Kansas and force election of a pro-slavery legislature.
1856 – The Treaty of Paris is signed, ending the Crimean War.
1861 – Discovery of the chemical elements: Sir William Crookes announces his discovery of thallium.
1863 – Danish prince Wilhelm Georg is chosen as King George of Greece.
1867 – Alaska is purchased from Russia for $7.2 million, about 2-cent/acre ($4.19/km²), by United States Secretary of State William H. Seward.
1870 – Texas is readmitted to the Union following Reconstruction.
1885 – The Battle for Kushka triggers the Panjdeh Incident which nearly gives rise to war between the Russian and British Empire.
1899 – German Society of Chemistry issues an invitation to other national scientific organizations to appoint delegates to the International Committee on Atomic Weights.
1912 – Sultan Abd al-Hafid signs the Treaty of Fez, making Morocco a French protectorate.
1918 – Outburst of bloody March Events in Baku and other locations of Baku Governorate.
1939 – The Heinkel He 100 fighter sets a world airspeed record of 463 mph (745 km/h).
1940 – Second Sino-Japanese War: Japan declares Nanking capital of a new Chinese puppet government, nominally controlled by Wang Jingwei.
1944 – World War II: Allied bombers conduct their most severe bombing run on Sofia, Bulgaria.
1944 – Out of 795 Lancasters, Halifaxes and Mosquitos sent to attack Nuremberg, 95 bombers do not return, making it the largest RAF Bomber Command loss of the war.
1945 – World War II: Soviet forces invade Austria and capture Vienna; Polish and Soviet forces liberate Danzig.
1949 – Cold War: A riot breaks out in Austurvöllur square in Reykjavík, when Iceland joins NATO.
1961 – The Single Convention on Narcotic Drugs is signed in New York City.
1965 – Vietnam War: A car bomb explodes in front of the United States Embassy, 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 Member of Parliament, is killed by a car bomb as he exits the Palace of Westminster. The Irish National Liberation Army claims responsibility.
1981 – U.S. President Ronald Reagan is shot in the chest outside a Washington, D.C., hotel by John Hinckley, Jr.; three others are wounded in the same incident.
1982 – Space Shuttle program: STS-3 Mission is completed with the landing of Columbia at White Sands Missile Range, New Mexico.
2009 – Twelve gunmen attack the Manawan Police Academy in Lahore, Pakistan.
2017 – SpaceX conducts the world’s first reflight of an orbital class rocket.