- Dec 1 1st US helium-filled dirigible makes its 1st flight
- Dec 1 US Post Office establishes philatelic agency
- Dec 3 CFL Grey Cup, Varsity Stadium, Toronto: Toronto Argonauts win 2nd Championship; beat Edmonton Eskimos, 23-0
- Dec 4 American Professional Football Association Championship, Cubs Park, Chicago: Chicago Staleys beat Buffalo All-Americans, 10-7 in de facto championship game after teams tied in standings
- Dec 4 The Virginia Rappe manslaughter trial against Roscoe 'Fatty' Arbuckle ends in a hung jury
Anglo-Irish Treaty Signed
Dec 6 Anglo-Irish Treaty signed; Ireland receives dominion status; partition creates Northern Ireland
Liberal Party Victory
Dec 6 Canada's Liberal Party and its leader Mackenzie King defeats Arthur Meighen's Conservative Party and Thomas Crerar' Progressive Party in general election, goes on to form a minority government
- Dec 7 KWG-AM in Stockton CA begins radio transmissions
Valera Rejects Anglo-Irish Treaty
Dec 8 Eamon de Valera publicly repudiates Anglo-Irish Treaty
Anglo-Irish Treaty Ratified
Dec 16 The Anglo-Irish Treaty, agreed to by the British Parliament and Sinn Féin, is ratified
- Dec 16 The Communist Party of South Africa (CPSA) calls for a united front in a pass burning campaign on Dingaan's Day
World Series Best-of-7
Dec 20 AL votes to return to best-of-7 World Series, while NL votes best-of-9; Commissioner Kenesaw Mountain Landis casts deciding vote for best-of-7
- Dec 21 Supreme Court rules Arizona statute protecting labor rights to picket and insulating disputes from court injunctions is unconstitutional
Carlo Gambino Enters US
Dec 23 Gangster Carlo Gambino enters the United States as an illegal immigrant on the SS Vincenzo Florio
Visva-Bharati University Inaugurated
Dec 23 Visva-Bharati University is inaugurated in Santiniketan, West Bengal, India, founded by Rabindranath Tagore
- Dec 24 Ottawa’s Harry Broadbent scores in 10-0 Senators blowout of the Montreal Canadiens; first in 16-game NHL record goal-scoring streak; Charlie Simmer’s 13 game streak (1979) is considered modern-day record
- Dec 25 Last major Potlatch (ceremony) by Chief Daniel Cranmer (Kwakwaka’wakw) from Alert Bay, British Columbia. Twenty-six people arrested, their masks and regalia sold by Canadian government. [1]
- Dec 28 The beginning of the Rand Rebellion in Southern Africa; the rebellion started as a strike by white mineworkers on and became an open armed rebellion against the state
- Dec 29 Mackenzie King is sworn in as the 10th Prime Minister of Canada
- Dec 31 Australasian Championships Men's Tennis, Perth: Australian Rhys Gemmell beats countryman Alf Hedeman 7-5, 6-1, 6-4
- Dec 31 Last San Francisco firehorses retired
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