1st January » The Belorussian Communist Organisation is founded as a separate party.
2nd January » The second Palmer Raids e.g Palmer Raid takes place with another 6,000 suspected communists and anarchists arrested and held without trial. These raids take place in several U.S. cities.
7th January » The New York State Assembly refuses to seat five duly elected Socialist Party of America named Socialist assemblymen.
8th January » The steel strike of 1919 ends in a complete failure for the Amalgamated Association of Iron and Steel Workers named Amalgamated Association of Iron, Steel and Tin Workers labor union.
10th January » The Treaty of Versailles takes effect, officially ending World War I.
16th January » Zeta Phi Beta Sorority Incorporated was founded on the campus of Howard University.
16th January » The League of Nations holds its first council meeting in Paris known as Paris, France.
19th January » The United States Senate votes against joining the League of Nations.
20th January » The American Civil Liberties Union is founded.
23rd January » The Netherlands refuses to surrender the exiled Wilhelm II, German Emperor named Kaiser Wilhelm II of Germany to the Allies of World War I named Allies.
26th January » Former Ford Motor Company executive Henry Leland launches the Lincoln Motor Company which he later sold to his former employer.
1st February » The Royal Canadian Mounted Police begins operations.
2nd February » The Treaty of Tartu (Russian–Estonian) named Tartu Peace Treaty is signed between Estonia and Russia.
2nd February » France occupies Klaipėda called Memel.
9th February » Under the terms of the Svalbard Treaty, international diplomacy recognizes Norwegian sovereignty over Arctic archipelago Svalbard, and designates it as demilitarized.
13th February » The Negro National League (1920–1931) known as Negro National League is formed.
14th February » The League of Women Voters is founded in Chicago.
29th February » Czechoslovakia or Czechoslovak National assembly adopted the Czechoslovak Constitution of 1920 known as Constitution.
8th March » The Arab Kingdom of Syria, the first modern Arab state to come into existence, is established.
13th March » The Kapp Putsch briefly ousts the Weimar Republic government from Berlin.
19th March » The United States Senate rejects the Treaty of Versailles for the second time (the first time was on November 19, 1919).
22nd March » Azeri and Turkish army soldiers with participation of Kurdish gangs Shushi Massacres known as attacked the Armenian inhabitants of Shushi (Nagorno Karabakh).
28th March » Palm Sunday tornado outbreak of 1920 affects the Great Lakes region and Deep South states.
15th April » Two security guards are murdered during a robbery in South Braintree, Massachusetts. Anarchism known as Anarchists Sacco and Vanzetti would be convicted of and executed for the crime, amid much controversy.
23rd April » The Grand National Assembly of Turkey (TBMM) is founded in Ankara, Turkey. It denounces the government of Sultan Mehmed VI and announces the preparation of a Turkish Constitution of 1921 known as temporary constitution.
25th April » At the San Remo conference, the principal Allies of World War I named Allied Powers of World War I adopt a resolution to determine the allocation of Class "A" League of Nations mandates for administration of the former Ottoman Empire e.g Ottoman-ruled lan
28th April » Azerbaijan is added to the Soviet Union.
30th April » Peru becomes a signatory to the Buenos Aires Convention known as Buenos Aires copyright treaty.
2nd May » The first game of the Negro National League (1920-1931) called Negro National League baseball is played in Indianapolis.
3rd May » A 1920 Georgian coup attempt named Bolshevik coup fails in the Democratic Republic of Georgia.
5th May » Authorities arrest Nicola Sacco and Bartolomeo Vanzetti for alleged robbery and murder.
7th May » Treaty of Moscow (1920) called Treaty of Moscow: Russian SFSR named Soviet Russia recognizes the independence of the Democratic Republic of Georgia only to invade the country six months later.
7th May » The Art Gallery of Ontario, in Toronto, opens the first exhibition by the Group of Seven (artists) e.g Group of Seven.
9th May » Polish-Soviet War: The Polish army under General Edward Rydz-Śmigły celebrates its 1920 Kiev Offensive known as capture of Kiev with a victory parade on Khreschatyk.
16th May » In Rome, Pope Benedict XV Canonization of Joan of Arc called canonizes Joan of Arc.
20th May » Montreal, Quebec radio station XWA broadcasts the first regularly scheduled radio programming in North America.
4th June » Hungary loses 71% of its territory and 63% of its population when the Treaty of Trianon is signed in Paris.
11th June » During the 1920 Republican National Convention U.S. Republican National Convention in Chicago, Republican Party (United States) U.S. Republican Party leaders gathered in a room at the Blackstone Hotel to come to a consensus on their candidate for the Unit
15th June » A new border treaty between Germany and Denmark gives northern Duchy of Schleswig named Schleswig to Denmark.
11th July » In the East Prussian plebiscite the local populace decides to remain with Weimar Republic named Weimar Germany.
12th July » The Soviet–Lithuanian Peace Treaty is signed. Russian Soviet Federative Socialist Republic or Soviet Russia recognizes independent Lithuania.
15th July » The Second Polish Republic Polish Parliament establishes Silesian Voivodeship (1920–1939) Silesian Voivodeship before the Upper Silesia plebiscite Polish-German plebiscite.
29th July » Construction of the Link River Dam begins as part of the Klamath Project named Klamath Reclamation Project.
13th August » Polish–Soviet War: the Battle of Warsaw (1920) known as Battle of Warsaw begins and will last till August 25. The Red Army is defeated.
15th August » Polish–Soviet War: Battle of Warsaw (1920) e.g Battle of Warsaw, so-called Miracle at the Vistula.
16th August » Ray Chapman of the Cleveland Indians is hit on the head by a fastball thrown by Carl Mays of the New York Yankees, and dies early the next day. Chapman was the second player to die from injuries sustained in a Major League Baseball game, the first being D
16th August » The congress of the Communist Party of Bukhara opens. The congress would call for armed revolution.
16th August » Polish–Soviet War: The Battle of Radzymin (1920) known as Battle of Radzymin concludes; the Soviet Red Army is forced to turn away from Warsaw.
20th August » The first commercial radio station, 8MK (now WWJ (AM) named WWJ), begins operations in Detroit e.g Detroit, Michigan.
26th August » The Nineteenth Amendment to the United States Constitution e.g 19th amendment to United States Constitution takes effect, giving women the right to vote.
31st August » Polish-Bolshevik War: A decisive Poland e.g Polish victory in the Battle of Komarów.
31st August » The first radio news program is broadcast by WWJ (AM) called 8MK in Detroit, Michigan.
1st September » The 'Fountain of Time' opens as a tribute to the 100 years of peace between the United States and Great Britain following the Treaty of Ghent.
7th September » Two newly purchased Savoia-Marchetti or Savoia flying boats crash in the Swiss Alps en route to Finland where they would serve with the 'Suomen Ilmavoimat', killing both crews.
16th September » The Wall Street bombing: A bomb in a horse wagon explodes in front of the 23 Wall Street called J. P. Morgan building in New York City killing 38 and injuring 400.
1st October » Sir Percy Cox lands in Basra to assume his responsibilities as High Commissioner in Iraq.
10th October » The Carinthian Plebiscite determines that the larger part of Carinthia (duchy) e.g Carinthia should remain part of Austria.
14th October » Part of Pechengsky District named Petsamo Province is ceded by the Soviet Union to Finland.
25th October » After 74 days on Hunger Strike in Brixton Prison, England, the Sinn Féin Lord Mayor of Cork, Terence MacSwiney dies.
30th October » The Communist Party of Australia is founded in Sydney.
1st November » American Fishing Schooner Esperanto defeats the Canadian Fishing Schooner Delawana in the First International Fishing Schooner Championship Races in City of Halifax named Halifax.
2nd November » In the United States, KDKA (AM) known as KDKA of Pittsburgh, Pennsylvania starts broadcasting as the first commercial radio station. The first broadcast is the result of the United States presidential election, 1920.
2nd November » Adam Martin Wyant became the first former professional American football player United States House of Representatives elections, 1920 or to be elected to the United States Congress.
7th November » Patriarch Tikhon of Moscow named Tikhon issues a decree that leads to the formation of the Russian Orthodox Church Outside Russia.
12th November » Italy and the Kingdom of Yugoslavia called Kingdom of Serbs, Croats and Slovenes sign the Treaty of Rapallo (1920) called Treaty of Rapallo.
15th November » First assembly of the League of Nations is held in Geneva, Switzerland.
21st November » Irish War of Independence: In Dublin, 31 people are killed in what became known as "Bloody Sunday (1920) named Bloody Sunday". This included fourteen British informants, fourteen Irish civilians and three Irish Republican Army prisoners.
28th November » Irish War of Independence: Kilmichael Ambush The Irish Republican Army ambush a convoy of British Auxiliary Division or Auxiliaries and kill seventeen.
2nd December » Following more than a month of Turkish-Armenian War, the Turkish dictated Treaty of Alexandropol is concluded.
5th December » Dimitrios Rallis forms a government in Kingdom of Greece e.g Greece.
11th December » Irish War of Independence: In retaliation for an Irish Republican Army named IRA ambush, British forces The Burning of Cork e.g burn and loot numerous buildings in Cork city. Many civilians also reported being beaten, shot at, robbed and verbally abused b
19th December » Constantine I of Greece King Constantine I is restored as Kingdom of Greece King of the Hellenes after the death of his son Alexander of Greece and a Referendum plebiscite.
22nd December » The GOELRO plan known as GOELRO economic development plan is adopted by the 8th Congress of Soviets e.g Congress of Soviets of the Russian SFSR.