October 9 is the 282nd day of the year (283rd in leap years) in the Gregorian calendar; 83 days remain until the end of the year.
1604 – Kepler's Supernova is the most recent supernova to be observed within the Milky Way.
1635 – Roger Williams is banished from the Massachusetts Bay Colony after religious and policy disagreements.
1701 – The Collegiate School of Connecticut (later renamed Yale University) is chartered in Old Saybrook.
1708 – Peter the Great defeats the Swedes at the Battle of Lesnaya.
1740 – Dutch colonists and Javanese natives begin a massacre of the ethnic Chinese population in Batavia, eventually killing at least 10,000.
1760 – Seven Years' War: Russian and Austrian troops briefly occupy Berlin.
1790 – A severe earthquake in northern Algeria causes severe damage and a tsunami in the Mediterranean Sea and kills 3,000.
1799 – HMS Lutine sinks with the loss of 240 men and a cargo worth 1.2 million pounds British currency.
1812 – War of 1812: In a naval engagement on Lake Erie, American forces capture two British ships: HMS Detroit and HMS Caledonia.
1825 – Restauration arrives in New York Harbor from Norway, the first organized immigration from Norway to the United States.
1834 – Opening of the Dublin and Kingstown Railway, the first public railway on the island of Ireland.
1847 – Slavery is abolished in the Swedish colony of Saint Barthélemy.
1861 – American Civil War: Union troops repel a Confederate attempt to capture Fort Pickens at the Battle of Santa Rosa Island.
1864 – American Civil War: Union cavalrymen defeat Confederate forces at Toms Brook, Virginia.
1873 – A meeting at the U.S. Naval Academy establishes the U.S. Naval Institute.
1911 – An accidental bomb explosion triggers the Wuchang Uprising against the Qing dynasty, beginning the Xinhai Revolution.