- Sep 1 Belgian boxer Gustave Roth beats Heinz Lazek of Austria in a 15 round points decision to win the EBU and vacant IBU world light heavyweight title in Vienna
- Sep 2 First transatlantic "ping-pong" round-trip air flight from New York to England and back begins, piloted by Dick Merrill with Harry Richman
- Sep 2 NFL Chicago College All-Star Game: All-Stars 7, Detroit Lions 7; 76,000 at Soldier Field
- Sep 3 For the first and only time in the history of the Walker Cup golf event, there is a shutout; the United States routs Great Britain, 9-0 at Pine Valley GC in New Jersey
Battle of Talavera de la Reina
Sep 3 Francisco Franco's troops conquer Irun and Talavera de la Reina, Spain
Swing Time
Sep 4 RKO Radio Pictures releases "Swing Time", directed by George Stevens, starring Fred Astaire and Ginger Rogers
- Sep 7 The last surviving member of the marsupial thylacine species, Benjamin, dies alone in his/her cage at the Hobart Zoo (Hobart, Tasmania, Australia)
Dutch Princess Engaged
Sep 8 Princess Juliana of The Netherlands & German prince Bernard Lippe-Biesterfeld become engaged
US Open Women's Tennis
Sep 12 50th US National Championship Women's Tennis, Forest Hills, NY: #3 seed Alice Marble beats top seeded fellow American Helen Jacobs 4-6, 6-3, 6-2
US Men's Tennis Open
Sep 12 US National Championship Men's Tennis: Englishman Fred Perry wins his 8th and final Grand Slam event before turning pro; beats American Don Budge 2-6, 6-2, 8-6, 1-6, 10-8
Feller's Strike Out Record
Sep 13 17-year-old Cleveland Indians future Baseball HOF pitcher Bob Feller strikes out then record 17 Philadelphia A's in 5-2 win at League Park, Cleveland
Murder Inc, kills Rosen
Sep 13 Acting on the orders of Louis Buchalter, Murder Inc. killers gun down Joseph Rosen, a Brooklyn candy store owner
- Sep 14 1st prefrontal lobotomy in America performed by Walter Freeman and James W. Watts at George Washington University Hospital in Washington D.C.
Waner Ties Hornsby Record
Sep 14 Pittsburgh Pirates' future Baseball Hall of Fame outfielder Paul Waner ties Rogers Hornsby's NL record of 200 MLB hits for 7th time
- Sep 21 Spanish fascist junta names Francisco Franco to Generalissimo and Supreme Commander
- Sep 25 Joe Medwick sets a still-standing NL record with his 64th double
- Sep 27 Boston Redskins and Brooklyn Dodgers play one of only 4 penalty free games in NFL history; Boston wins 14-3 at Ebbets Field, Brooklyn
Walter Alston
Sep 27 First baseman Walter Alston plays in his only major league game for the St. Louis Cardinals; later manages Brooklyn/Los Angeles Dodgers for 23 years
- Sep 27 Francisco Franco's nationalist Army of Africa captures the Alcázar of Toledo after a two month siege
- Sep 27 Netherlands leave Gold Standard/devaluate guilder
- Sep 28 Bachelor's Children debuts on CBS radio (at 9:45 am)
- Sep 29 Radio used for 1st time for a presidential campaign
- Sep 30 International Commission of Straits (Dardanelles & Bosphorus) ends
- Sep 30 Pinewood Studios opens in Buckinghamshire England
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