April 20 events in history

1303 The Sapienza University of Rome is instituted by Pope Boniface VIII
1453 The last naval battle in Byzantine history occurs, as three Genoese galleys escorting a Byzantine transport fight their way through the huge Ottoman blockade fleet and into the Golden Horn
1534 Jacques Cartier begins the voyage during which he discovers Canada and Labrador
1535 The Sun dog phenomenon observed over Stockholm and depicted in the famous painting Vädersolstavlan
1653 Oliver Cromwell dissolves the Rump Parliament
1657 Admiral Robert Blake destroys a Spanish silver fleet under heavy fire at the Battle of Santa Cruz de Tenerife
1657 Freedom of religion is granted to the Jews of New Amsterdam (later New York City)
1689 The former king, James II of England, now deposed, lays siege to Derry
1752 Start of Konbaung–Hanthawaddy War, a new phase in the Burmese Civil War (1740–57)
1770 The Georgian king, Erekle II, abandoned by his Russian ally Count Totleben, wins a victory over Ottoman forces at Aspindza
1775 American Revolutionary War: the Siege of Boston begins, following the battles at Lexington and Concord
1789 President George Washington arrives in Philadelphia after his inauguration to elaborate welcome at Gray's Ferry just after noon first inauguration of George Washington
1792 France declares war against the "King of Hungary and Bohemia", the beginning of French Revolutionary Wars
1809 Two Austrian army corps in Bavaria are defeated by a First French Empire army led by Napoleon I of France at the Battle of Abensberg on the second day of a four-day campaign that ended in a French victory
1810 The Governor of Caracas declares independence from Spain
1818 The case of Ashford v Thornton ends, with Abraham Thornton allowed to go free rather than face a retrial for murder, after his demand for trial by battle is upheld
1828 René Caillié becomes the first non-Muslim to enter Timbouctou
1836 U.S. Congress passes an act creating the Wisconsin Territory
1861 American Civil War: Robert E. Lee resigns his commission in the United States Army in order to command the forces of the state of Virginia
1862 Louis Pasteur and Claude Bernard complete the experiment falsifying the theory of spontaneous generation
1865 Astronomer Pietro Angelo Secchi demonstrates the Secchi disk, which measures water clarity, aboard Pope Pius IX's yacht, the L'Immaculata Concezion
1871 The Civil Rights Act of 1871 becomes law
1876 The April Uprising, a key point in modern Bulgarian history, leading to the Russo-Turkish War and the liberation of Bulgaria from domination as an independent part of the Ottoman Empire
1884 Pope Leo XIII publishes the encyclical Humanum Genus
1902 Pierre and Marie Curie refine radium chloride
1908 Opening day of competition in the New South Wales Rugby League
1912 Opening day for baseball's Tiger Stadium in Detroit, Michigan, and Fenway Park in Boston
1914 Nineteen men, women, and children die in the Ludlow Massacre during a Colorado coal-miner's strike
1916 The Chicago Cubs play their first game at Weeghman Park (currently Wrigley Field), defeating the Cincinnati Reds 7–6 in 11 innings
1918 Manfred von Richthofen, aka The Red Baron, shoots down his 79th and 80th victims, his final victories before his death the following day
1922 The Soviet government creates South Ossetian Autonomous Oblast within Georgian SSR
1926 Western Electric and Warner Bros. announce Vitaphone, a process to add sound to film
1939 Adolf Hitler's 50th birthday is celebrated as a national holiday in Nazi Germany
1939 Billie Holiday records the first civil rights song "Strange Fruit"
1945 World War II: US troops capture Leipzig, Germany, only to later cede the city to the Soviet Union
1945 World War II: Führerbunker: Adolf Hitler makes his last trip to the surface to award Iron Crosses to boy soldiers of the Hitler Youth
1945 Twenty Jewish children used in medical experiments at Neuengamme are killed in the basement of the Bullenhuser Damm school
1946 The League of Nations officially dissolves, giving most of its power to the United Nations
1951 Dan Gavriliu performs the first surgical replacement of a human organ
1961 Failure of the Bay of Pigs Invasion of US-backed Cuban exiles against Cuba
1964 BBC Two launches with a power cut because of the fire at Battersea Power Station
1968 English politician Enoch Powell makes his controversial Rivers of Blood speech
1972 Apollo 16, commanded by John Young, lands on the moon
1978 Korean Air Lines Flight 902 is shot down by the Soviet Union
1980 Climax of Berber Spring in Algeria as hundreds of Berber political activists are arrested
1984 The Good Friday Massacre, an extremely violent ice hockey playoff game, is played in Montreal, Canada
1985 The ATF raids The Covenant, The Sword, and the Arm of the Lord compound in northern Arkansas
1986 Pianist Vladimir Horowitz performs in his native Russia for the first time in 61 years
1998 German terrorist group the Red Army Faction announces their dissolution after 28 years
1999 Columbine High School massacre: Eric Harris and Dylan Klebold killed 13 people and injured 24 others before committing suicide at Columbine High School in Columbine, Colorado