- Dec 1 School bus & train collide in Salt Lake City Utah
- Dec 2 The first 'Kindertransport' carrying Jewish refugee children from Nazi Germany arrives in Britain
- Dec 3 AAUs decides to continue linear measuring system over metric
- Dec 6 117 Spanish knights under capt Piet Laros return to Netherlands
- Dec 6 French-German friendship treaty drawn up (Ribbentrop-Bonnet Pact)
- Dec 7 Philip Barry's play "Here Come the Clowns" premieres in NYC
- Dec 7 W9XZY broadcasts facsimile of St Louis Post-Dispatch by radio
- Dec 8 Highest temperature for December in US recorded in La Mesa Calif
- Dec 9 1939 NFL Draft: Ki Aldrich from TCU first pick by Chicago Cardinals
- Dec 9 State of California uses gas chamber instead of hanging for 2nd time in a week: Wesley Eudy and Fred Barnes executed for roles in Folsom Prison escape attempt resulting in murder of warden and guard (San Quentin State Prison, Marin County)
- Dec 10 CFL Grey Cup: In repeat of last year, Toronto Argonauts defeat Winnipeg Blue Bombers, 30-7 to retain Championship
Fermi Awarded Physics Nobel
Dec 10 Italian scientist Enrico Fermi receives the Nobel Prize for Physics (work on reduced radioactivity)
- Dec 10 Ruth Fuller Sasaki, Zen teacher, Rinzai line, enters Zen priesthood
NY Giants vs. Green Bay Packers
Dec 11 National Football League Championship, Polo Grounds, NYC: New York Giants beat Green Bay Packers, 23-17; record title game attendance 48,120
Standard Ball for MLB
Dec 14 Major League Baseball agrees on use of a standard ball; disagrees on increasing rosters from 23 to 25 players, although Commissioner Kenesaw Mountain Landis eventually decides on 25
- Dec 14 Will Harridge is elected to a 10-year-term as AL president
- Dec 15 Groundbreaking begins for Jefferson Memorial in Washington, D.C.
Cross of Honour of the German Mother
Dec 16 Adolf Hitler institutes the state decoration and civil order of merit, Cross of Honour of the German Mother
- Dec 16 State of California executes Ed Davis (38), leader of Folsom Prison escape attempt resulting in murder of warden and guard (San Quentin State Prison, Marin County)
- Dec 17 Discovery of nuclear fission using uranium by Otto Hahn and his assistant Fritz Strassmann
- Dec 17 Utrecht Central Station destroyed by fire
- Dec 20 Boston Bruins rookie goalie Frankie Brimsek records his 3rd straight shutout with a 3-0 win over the New York Americans, making it his incredible sixth shutout in his first 8 NHL games
- Dec 23 Discovery of the first modern coelacanth in South Africa
Wizard of Oz Costume Catches Fire
Dec 23 Margaret Hamilton's costume catches fire while filming "The Wizard of Oz"
Vivian Leigh to Play Scarlet O'Hara
Dec 25 George Cukor announces Vivien Leigh will play Scarlett O'Hara in "Gone With The Wind"
- Dec 26 Tom Goddard takes a cricket hat-trick for England v South Africa
- Dec 28 Paul Gibb scores 106 on Test Cricket debut v South Africa
- Dec 29 Construction on Lake Washington Floating Bridge, Seattle, begins
- Dec 31 Daniel Sternefeld conducts premiere of his ballet "Pierlala" at the Royal Flemish Opera of Antwerp; choreographer Wladimir Karnetzky also danced the title role
- Dec 31 Dr R N Harger's "drunkometer", 1st breath test, introduced in Indiana
- Dec 31 Dutch national debt hits ƒ3,986,629,805.70
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