September 20 events in history

622 Muhammad and Abu Bakr arrived Medina
1058 Agnes of Poitou and Andrew I of Hungary meet to negotiate about the border-zone in present-day Burgenland
1066 Battle of Fulford, Viking Harald Hardrada defeats earls Morcar and Edwin
1187 Saladin begins the Siege of Jerusalem
1260 The Great Prussian Uprising among the old Prussians begins against the Teutonic Knights
1378 Cardinal Robert of Geneva, called by some the "Butcher of Cesena", is elected as Avignon Pope Clement VII, beginning the Papal schism
1498 The 1498 Nankai earthquake generates a tsunami that washes away the building housing the statue of the Great Buddha at Kōtoku-in in Kamakura, Kanagawa, Japan; since then the Buddha has sat in the open air
1519 Ferdinand Magellan sets sail from Sanlúcar de Barrameda with about 270 men on his expedition to circumnavigate the globe
1596 Diego de Montemayor founds the city of Monterrey in New Spain
1697 The Treaty of Ryswick is signed by France, England, Spain, the Holy Roman Empire and the Dutch Republic ending the Nine Years' War (1688–97)
1737 The finish of the Walking Purchase which forces the cession of 1.2 million acres (4,860 km²) of Lenape-Delaware tribal land to the Pennsylvania Colony
1792 French troops stop allied invasion of France, during the War of the First Coalition at Valmy
1835 Ragamuffin rebels capture Porto Alegre, then capital of the Brazilian imperial province of Rio Grande do Sul, triggering the start of ten-year-long Ragamuffin War
1848 The American Association for the Advancement of Science is created
1854 Battle of Alma: British and French troops defeat Russians in the Crimea
1857 The Indian Rebellion of 1857 ends with the recapture of Delhi by troops loyal to the East India Company
1860 The Prince of Wales (later King Edward VII of the United Kingdom) visits the United States
1863 American Civil War: The conclusion of the Battle of Chickamauga in northwestern Georgia, the bloodiest two-day battle of the conflict, and the only significant Confederate victory in the war's Western Theater
1870 Bersaglieri corps enter Rome through the Porta Pia and complete the unification of Italy
1871 Bishop John Coleridge Patteson is martyred on the island of Nukapu, a Polynesian outlier island now in the Temotu Province of the Solomon Islands. He is the first bishop of Melanesia
1881 Chester A. Arthur is inaugurated as the 21st President of the United States following the assassination of James Garfield
1893 Charles Duryea and his brother road-test the first American-made gasoline-powered automobile
1906 Cunard Line's RMS Mauretania is launched at the Swan Hunter & Wigham Richardson shipyard in Newcastle upon Tyne, England
1909 The Parliament of the United Kingdom passes the South Africa Act 1909, creating the Union of South Africa from the British Colonies of the Cape of Good Hope, Natal, Orange River Colony, and the Transvaal Colony
1910 The ocean liner SS France, later known as the "Versailles of the Atlantic", is launched
1911 White Star Line's RMS Olympic collides with British warship HMS Hawke
1920 Foundation of the Spanish Legion
1930 Syro-Malankara Catholic Church is formed by Archbishop Mar Ivanios
1942 Holocaust in Letychiv, Ukraine. In the course of two days the German SS murders at least 3,000 Jews
1946 The first Cannes Film Festival is held, having been delayed seven years due to World War II
1961 Greek general Konstantinos Dovas becomes Prime Minister of Greece
1962 James Meredith, an African American, is temporarily barred from entering the University of Mississippi
1967 RMS Queen Elizabeth 2 is launched at John Brown & Company, Clydebank, Scotland. It is operated by the Cunard Line
1970 Syrian tanks roll into Jordan in response to continued fighting between Jordan and the fedayeen
1971 Having weakened after making landfall in Nicaragua the previous day, Hurricane Irene regains enough strength to be renamed Hurricane Olivia, making it the first known hurricane to cross from the Atlantic Ocean into the Pacific
1973 Billie Jean King beats Bobby Riggs in the Battle of the Sexes tennis match at the Houston Astrodome
1977 The Socialist Republic of Vietnam is admitted to the United Nations
1979 A coup d'état in the Central African Empire overthrows Emperor Bokasa I
1982 The National Football League players begin a 57-day strike
1984 A suicide bomber in a car attacks the U.S. embassy in Beirut, Lebanon, killing twenty-two people
1985 Capital gains tax is introduced in Australia, one of a number of tax reforms by the Hawke/Keating government
1990 South Ossetia declares its independence from Georgia
2000 The United Kingdom's MI6 Secret Intelligence Service building is attacked by individuals using a Russian-built RPG-22 anti-tank missile. The perpetrators remain unidentified
2001 In an address to a joint session of Congress and the American people, U.S. President George W. Bush declares a "War on Terror"
2002 The Kolka-Karmadon rock/ice slide
2003 Maldives civil unrest: the death of prisoner Hassan Evan Naseem sparks a day of rioting in Malé
2007 Between 15,000 and 20,000 protesters marched on Jena, Louisiana, in support of six black youths who had been convicted of assaulting a white classmate
2008 A dump truck full of explosives detonates in front of the Marriott hotel in Islamabad, Pakistan, killing 54 people and injuring 266 others
2011 The United States military ends its "don't ask, don't tell" policy, allowing gay men and women to serve openly for the first time