Editing 1821 (section)

=== October–December ===
[[File:Η πολιορκία της Τριπολιτσάς.jpg|200px|thumb|right|[[October 5]] (September 23 [[Julian calendar|Greek calendar]]): The [[Siege of Tripolitsa]] by Greek rebels is followed by a massacre.]]
* [[September 23]] ([[Julian calendar|O.S.]])/[[October 5]] ([[Gregorian calendar|N.S.]]) – The [[Siege of Tripolitsa]] ends when Greek rebels capture the city of [[Tripoli, Greece]]; the massacre of 8,000 civilians follows. (Greek forces under the command of General [[Theodoros Kolokotronis]] have besieged the city for several months during the [[Greek War of Independence]] from Turkey and the Ottoman Empire.)<ref>{{Cite book|first=Benjamin|last=Lieberman|year=2013|title=Terrible Fate: Ethnic Cleansing in the Making of Modern Europe|publisher=Rowman & Littlefield|page=9}}</ref><ref>{{Cite book|editor=Tucker, Spencer C.|year=2009|title=A Global Chronology of Conflict: From the Ancient World to the Modern Middle East|publisher=ABC-CLIO|page=1139}}</ref>
* [[October 8]] ([[Julian calendar|O.S.]])/[[October 20]] ([[Gregorian calendar|N.S.]]) – Tsar [[Alexander I of Russia]] issues an imperial [[ukase]] guaranteeing freedom of commerce in Russia by merchants from [[Persia]].<ref>"Commerce between Russia and Persia— Proposed Union of the Black Sea with the Atlantic". ''The Oriental Herald'' (November 1826) p. 285.</ref>
* [[November 16]] – [[American Old West]]: The [[Santa Fe Trail]] is first used by [[William Becknell]].
* [[November 28]] – Panama [[Independence Act of Panama|declares independence]] from Spain, joining [[Gran Colombia]].
* [[December 1]] – [[History of the Dominican Republic]]: On the Caribbean island of [[Hispaniola]], General [[José Núñez de Cáceres]] ends the ''[[España Boba]]'' era of Spanish rule in the Captaincy General of Santo Domingo by establishing the [[Republic of Spanish Haiti]]. It will last for three months before being invaded by Haiti.
* [[December 6]] – The [[South Orkney Islands]] are discovered by seal hunters [[George Powell (sealer)|George Powell]] and [[Nathaniel Palmer]].<ref>{{Cite book|last=Headland | first = Robert K. |title= Chronological list of Antarctic expeditions and related historical events |publisher=Cambridge University Press|year= 1989|isbn=978-0-521-30903-5|oclc= 185311468}}</ref><ref>{{Cite encyclopedia|title= South Orkney Islands|url= https://www.britannica.com/EBchecked/topic/556316/South-Orkney-Islands|encyclopedia=[[Encyclopædia Britannica]] | edition = Online Academic}}</ref>
* [[December 15]] – The world's first geographical society, the ''[[Société de géographie]]'', is established in Paris.
* [[December 19]] – The [[Eyjafjallajökull]] volcano in Iceland begins to erupt.