September 20 is the 263rd day of the year (264th in leap years) in the Gregorian calendar; 102 days remain until the end of the year.
1187 - Saladin begins the Siege of Jerusalem.
1519 - Ferdinand Magellan sets sail from Sanlucar de Barrameda with about 270 men on his expedition which ultimately culminates in the first circumnavigation of the globe.
1737 - The Walking Purchase concludes, which forces the cession of 1.2 million acres of Lenape-Delaware tribal land to the Pennsylvania Colony.
1854 - Crimean War: British and French troops defeat Russians at the Battle of Alma.
1860 - The future King Edward VII of the United Kingdom begins the first visit to North America by a Prince of Wales.
1863 - American Civil War: The Battle of Chickamauga, in northwestern Georgia, ends in a Confederate victory.
1881 - U.S. President Chester A. Arthur is sworn in upon the death of James A. Garfield the previous day.[9] 1911 - The White Star Line's RMS Olympic collides with the British warship HMS Hawke.
1920 - Irish War of Independence: British police known as 'Black and Tans' burn the town of Balbriggan and kill two local men in revenge for an IRA assassination.
1941 - The Holocaust in Lithuania: Lithuanian Nazis and local police begin a mass execution of 403 Jews in NemenCine.
1946 - The first Cannes Film Festival is held, having been delayed for seven years due to World War II.
1962 James Meredith, an African American, is temporarily barred from entering the University of Mississippi.
1973 - Billie Jean King beats Bobby Riggs in the Battle of the Sexes tennis match at the Houston Astrodome 1973 - Singer Jim Croce, songwriter and musician Maury Muehleisen and four others die when their light aircraft crashes on takeoff at Natchitoches Regional Airport in Louisiana 1984- A suicide bomber in a car attacks the U.S. embassy in Beirut, Lebanon, killing twenty-two people 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' Born on this date 1917 - Red Auerbach, American basketball player and coach (d. 2006) 1934 - Sophia Loren, Italian actress