1780

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File:Treason of Arnold Arnold persuades Andre to conceal the papers in his boot - - painted by C.F. Blauvelt. LCCN2010651755.jpg

September 21: American Major General Benedict Arnold, commander of West Point, commits treason by supplying information to Britain's Major John Andre.

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File:Waxhaw massacre sketch.jpg

May 29: Waxhaw Massacre in America.

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Events

January–March

January 16 – American Revolutionary War – Battle of Cape St. Vincent: British Admiral Sir George Rodney defeats a Spanish fleet.
February 19 – The legislature of New York votes to allow its delegates to cede a portion of its western territory to the Continental Congress for the common benefit of the war.<ref name="Harper1780">Template:Cite book</ref>
March 1 – The legislature of Pennsylvania votes, 34 to 21, to approve An Act for the Gradual Abolition of Slavery.<ref name=Ferguson>Template:Cite book</ref>
March 11
- The First League of Armed Neutrality is formed by Russia with Denmark and Sweden to try to prevent the British Royal Navy from searching neutral vessels for contraband (February 28 O.S.).
- General Lafayette embarks on Template:Ship at Rochefort, arriving in Boston on April 28, carrying the news that he has secured French men and ships to reinforce the American side in the American Revolutionary War.
March 17 – American Revolutionary War: The British San Juan Expedition sails from Jamaica under the command of Captains John Polson and Horatio Nelson to attack the Captaincy General of Guatemala (modern-day Nicaragua) in New Spain.
March 26 – The British Gazette and Sunday Monitor, the first Sunday newspaper in Britain, begins publication.

April–June

April 16 – The University of Münster in Münster, North Rhine-Westphalia, Germany is founded.
April 29 – American Revolutionary War: The Spanish commander of the Fortress of the Immaculate Conception on the San Juan River in modern-day Nicaragua surrenders it to the British San Juan Expedition.
May 4 – The first Epsom Derby horse race is run on Epsom Downs, Surrey, England.<ref name="Cassell's Chronology_333">Template:Cite book</ref> The victor is Diomed.<ref name="Pocket On This Day">Template:Cite book</ref>
May 12 – American Revolutionary War: Charleston, South Carolina is taken by British forces after 44 days of siege.
May 13 – The Cumberland Compact is signed by American settlers, in the Cumberland Valley of Tennessee.
May 19 – New England's Dark Day: An unaccountable darkness spreads over New England, regarded by some observers as a fulfillment of Bible prophecy.<ref>Template:Cite book</ref><ref>Template:Cite book</ref>
May 29 – American Revolutionary War – Waxhaw Massacre: Loyalist forces under Colonel Banastre Tarleton kill surrendering American soldiers.
June 2 – An Anti-Catholic mob led by Lord George Gordon marches on the Parliament of Great Britain, leading to the outbreak of the Gordon Riots in London.<ref name="Pocket On This Day"/>
June 7 – The Gordon Riots in London are ended by the intervention of troops. About 285 people are shot dead, with another 200 wounded and around 450 arrested.
June 23 – American Revolutionary War – Battle of Springfield: The Continental Army defeats the British in New Jersey.

July–September

July 11 – French soldiers arrive in Newport, Rhode Island to reinforce the colonists, in the American Revolutionary War.<ref>{{#invoke:citation/CS1|citation

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July 17 – The first bank created in the United States, the Bank of Pennsylvania, is chartered.<ref name=Ferguson/>
August 9 – American Revolutionary War: Spanish admiral Luis de Córdova y Córdova captures a British convoy totalling 55 vessels amongst Indiamen, frigates and other cargo ships off Cape St. Vincent.<ref>Template:Cite book</ref><ref>Template:Cite book</ref>
August 16 – American Revolutionary War – Battle of Camden: British troops inflict heavy losses on a Patriot army at Camden, South Carolina.
August 24 – King Louis XVI abolishes the use of torture in extracting confessions in French law courts.
September 21 – Benedict Arnold gives detailed plans of West Point to Major John André. Three days later, André is captured, with papers revealing that Arnold was planning to surrender West Point to the British.
September 25 – Benedict Arnold flees to British-held New York.
September 29 – The Danish ship-of-the-line Printz Friderich runs aground on the Kobbergrund shoal and is a total loss

October–December

October 2 – American Revolutionary War: In Tappan, New York, British spy John André is hanged by American forces.
October 7 – American Revolutionary War: Battle of Kings Mountain: Patriot militia forces annihilate Loyalists under British Major Patrick Ferguson, at Kings Mountain, South Carolina.
October 10–16 – The Great Hurricane flattens the islands of Barbados, Martinique and Sint Eustatius; 22,000 are killed.
November 4 – Rebellion of Túpac Amaru II: In the Spanish Viceroyalty of Peru, Túpac Amaru II leads an uprising of Aymara and Quechua peoples and mestizo peasants as a protest against the Bourbon Reforms.
November 28 – A lightning strike in Saint Petersburg begins a fire that burns 11,000 homes.<ref>Template:Cite book</ref>
November 29 – Maria Theresa of Austria dies in Vienna after 40 years of rule, and her Habsburg dominions pass to her ambitious son, Joseph II, who has already been Holy Roman Emperor since 1765.
November 30 – American Revolutionary War: The British San Juan Expedition is forced to withdraw.
December 14 – Alexander Hamilton marries Elizabeth Schuyler Hamilton
December 16 – Emperor Kōkaku accedes to the throne of Japan.
December 20 – The Fourth Anglo-Dutch War begins.<ref>Template:Cite book</ref>

Date unknown

Jose Gabriel Kunturkanki, businessman and landowner, proclaims himself Inca Túpac Amaru II.
The Duke of Richmond calls, in the House of Lords of Great Britain, for manhood suffrage and annual parliaments, which are rejected.
Jeremy Bentham's Introduction to Principles of Morals and Legislation, presenting his formulation of utilitarian ethics, is printed (but not published) in London.
Nikephoros Theotokis starts introducing Edinoverie, an attempt to integrate the Old Believers into Russia's established church.
The Woodford Reserve bourbon whiskey distillery begins operation in Kentucky.
In Ireland, Lady Berry, who is sentenced to death for the murder of her son, is released when she agrees to become an executioner (she retires in 1810).
The Jameson Irish Whiskey distillery is founded in Dublin, Ireland.
The original Craven Cottage is built by William Craven, 6th Baron Craven, in London, on what will become the centre circle of Fulham F.C.'s pitch.
The amateur dramatic group Det Dramatiske Selskab is founded in Christiania, Norway.
Western countries pay 16,000,000 ounces of silver for Chinese goods.
The Kingdom of Great Britain reaches c.9 million population.