Iraq: Day of Saddam Hussein's downfall
1241 - Battle of Liegnitz: Mongol forces defeat the Polish and German armies.
1413 - Henry V is crowned King of England.
1440 - Christopher of Bavaria is appointed King of Denmark.
1682 - Robert Cavelier de La Salle discovers the mouth of the Mississippi River, claims it for France and names it Louisiana.
1860 - The oldest audible sound recording of a human voice is recorded.
1865 - Birth of Charles Proteus Steinmetz
1865 - American Civil War: Robert E. Lee surrenders the Army of Northern Virginia (26,765 troops) to Ulysses S. Grant at Appomattox Courthouse, Virginia, effectively ending the war.
1867 - Alaska purchase: Passing by a single vote, the United States Senate ratifies a treaty with Russia for the purchase of Alaska.
1909 - The U.S. Congress passes the Payne-Aldrich Tariff Act.
1916 - World War I: The Battle of Verdun – German forces launch their third offensive of the battle.
1917 - World War I: The Battle of Arras – the battle begins with Canadian Corps executing a massive assault on Vimy Ridge.
1918 - World War I: The Battle of the Lys – the Portuguese Expeditionary Corps is crushed by the German forces during what is called the Spring Offensive on the Belgian region of Flanders.
193 - Septimius Severus is proclaimed Roman Emperor by the army in Illyricum (in the Balkans).
1937 - The Kamikaze arrives at Croydon Airport in London – it is the first Japanese-built aircraft to fly to Europe.
1939 - Marian Anderson sings at the Lincoln Memorial, after being denied the right to sing at the Daughters of the American Revolution's Constitution Hall.
1940 - World War II: Germany invades Denmark and Norway.
1942 - World War II: The Battle of Bataan/Bataan Death March – United States forces surrender on the Bataan Peninsula. The Japanese Navy launches an air raid on Trincomalee in Ceylon (Sri Lanka); Royal Navy aircraft carrier HMS;Hermes and Royal Australian Navy Destroyer HMAS;Vampire are sunk off the island's east coast.
1945 - World War II: The German pocket battleship Admiral Scheer is sunk.
1945 - World War II: The Battle of Königsberg, in East Prussia, ends.
1945 - The United States Atomic Energy Commission is formed.
1947 - The Glazier-Higgins-Woodward tornadoes kill 181 and injure 970 in Texas, Oklahoma, and Kansas.
1947 - The Journey of Reconciliation, the first interracial Freedom Ride begins through the upper South in violation of Jim Crow laws. The riders wanted enforcement of the United States Supreme Court's 1946 Irene Morgan decision that banned racial segregation in interstate travel.
1948 - Jorge Eliécer Gaitán's assassination provokes a violent riot in Bogotá (the Bogotazo), and a further ten years of violence in Colombia known as La violencia.
1948 - Massacre at Deir Yassin.
1952 - Hugo Ballivian's government is overthrown by the Bolivian National Revolution, starting a period of agrarian reform, universal suffrage and the nationalisation of tin mines
1957 - The Suez Canal in Egypt is cleared and opens to shipping.
1959 - Mercury program: NASA announces the selection of the United States' first seven astronauts, whom the news media quickly dub the "Mercury Seven".
1965 - Astrodome opens. First indoor baseball game is played.
1967 - The first Boeing 737 (a 100 series) makes its maiden flight.
1968 - Martin Luther King funeral
1969 - The "Chicago Eight" plead not guilty to federal charges of conspiracy to incite a riot at the 1968 Democratic National Convention in Chicago, Illinois.
1969 - The first British-built Concorde 002 makes its maiden flight from Filton to RAF Fairford.
1975 - The first game of the Philippine Basketball Association, the second oldest professional basketball league in the world.
1989 - The April 9 tragedy in Tbilisi, Georgian SSR an anti-Soviet peaceful demonstration and hunger strikes, demanding restoration of Georgian independence is dispersed by the Soviet army, resulting in 20 deaths and hundreds of injuries.
1991 - Georgia declares its independence from the Soviet Union.
1992 - A U.S. Federal Court finds former Panamanian dictator Manuel Noriega guilty of drug and racketeering charges. He is sentenced to 30 years in prison.
1992 - John Major's Conservative Party wins an unprecedented fourth general election victory in the United Kingdom.
1999 - Ibrahim Baré Maïnassara, President of Niger, is assassinated.
2002 - The funeral of Queen Elizabeth, the Queen Mother at Westminster Abbey.
2003 - 2003 invasion of Iraq: Baghdad falls to American forces.
2005 - Charles, Prince of Wales marries Camilla Parker Bowles.