Historical Events on this Day in History - per Wikipedia

September 23

• 1122 – Pope Calixtus II and Holy Roman Emperor Henry V agree to the Concordat of Worms to put an end to the Investiture Controversy.
• 1409 – Battle of Kherlen, the second significant victory over Ming China by the Mongols since 1368.
• 1459 – Battle of Blore Heath, the first major battle of the English Wars of the Roses, is fought at Blore Heath in Staffordshire.
• 1641 – The Merchant Royal, carrying a treasure worth over a billion US dollars, is lost at sea off Land's End.
• 1642 – First commencement exercises occur at Harvard College.
• 1779 – American Revolution: a squadron commanded by John Paul Jones on board the USS Bonhomme Richard wins the Battle of Flamborough Head, off the coast of England, against two British warships.
• 1780 – American Revolution: British Major John André is arrested as a spy by American soldiers exposing Benedict Arnold's change of sides.
• 1803 – Second Anglo-Maratha War: Battle of Assaye between the British East India Company and the Maratha Empire in India.
• 1806 – Lewis and Clark return to St. Louis after exploring the Pacific Northwest of the United States.
• 1821 – Tripolitsa, Greece, falls and 30,000 Turks are massacred during the Greek War of Independence.
• 1845 – The Knickerbockers Baseball Club, the first baseball team to play under the modern rules, is founded in New York.
• 1846 – Neptune is discovered by French astronomer Urbain Jean Joseph Le Verrier and British astronomer John Couch Adams; the discovery is verified by German astronomer Johann Gottfried Galle.
• 1857 – The Russian warship Lefort capsizes and sinks during a storm in the Gulf of Finland, killing all 826 aboard.
• 1868 – Grito de Lares ("Lares Revolt") occurs in Puerto Rico against Spanish rule.
• 1889 – Nintendo Koppai (Later Nintendo Company, Limited) is founded by Fusajiro Yamauchi to produce and market the playing card game Hanafuda.
• 1905 – Norway and Sweden sign the "Karlstad treaty", peacefully dissolving the Union between the two countries.
• 1908 – University of Alberta in Alberta, Canada, is founded.
• 1909 – The Phantom of the Opera (original title: Le Fantôme de l'Opéra), a novel by French writer Gaston Leroux, is first published as a serialization in Le Gaulois.
• 1932 – The Kingdom of Hejaz and Nejd is renamed the Kingdom of Saudi Arabia.
• 1936 – First ascent of Siniolchu by a German team.
• 1938 – Mobilization of the Czechoslovak army in response to the Munich Crisis.
• 1941 – World War II: The first gas chamber experiments are conducted at Auschwitz.
• 1942 – World War II: First day of the September Matanikau action on Guadalcanal as United States Marine Corps forces attack Imperial Japanese Army units along the Matanikau River.
• 1943 – World War II: The so-called Salò Republic is born.
• 1952 – Richard Nixon makes his "Checkers speech".
• 1959 – Iowa farmer and corn breeder Roswell Garst hosts Soviet premier Nikita Khrushchev.
• 1959 – The MS Princess of Tasmania, Australia’s first passenger roll-on/roll-off diesel ferry, makes her maiden voyage across Bass Strait.
• 1962 – The Lincoln Center for the Performing Arts in New York City opens with the completion of the first building, the Philharmonic Hall (now Avery Fisher Hall) home of the New York Philharmonic.
• 1969 – The Chicago Eight trial opens in Chicago.
• 1972 – Philippine President Ferdinand Marcos announces over television and radio the implementation of martial law.
• 1973 – Juan Perón returns to power in Argentina.
• 1983 – Saint Kitts and Nevis joins the United Nations.
• 1983 – Gerrie Coetzee of South Africa becomes the first African boxing world heavyweight champion.
• 1983 – Gulf Air Flight 771 is bombed, killing all 117 people on board.
• 1986 – Jim Deshaies of the Houston Astros sets the major-league record by striking out the first eight batters of the game against the Los Angeles Dodgers.
• 1988 – José Canseco of the Oakland Athletics becomes the first member of the 40-40 club.
• 1992 – A large Provisional Irish Republican Army bomb destroys forensic laboratories in Belfast.
• 1999 – Celebrate Bisexuality Day was first observed in the United States.
• 1999 – NASA announces that it has lost contact with the Mars Climate Orbiter.
• 1999 – Qantas Flight 1 overruns the runway in Bangkok during a storm. Although some passengers only receive minor injuries, it is still the worst crash in Qantas's history since 1960.
• 2002 – The first public version of the web browser Mozilla Firefox ("Phoenix 0.1") is released.
• 2004 – Hurricane Jeanne: At least 1,070 in Haiti are reported to have been killed by floods.
• 2008 – Kauhajoki school shooting: Matti Saari kills 10 people before committing suicide.