- Sep 2 W Somerset Maugham's "East of Suez" premieres in London
- Sep 4 Last day of Julian civil calendar (in parts of Bulgaria)
- Sep 4 Man o' War wins the 1 5/8-mile Lawrence Realization Stakes at Belmont Park by 100 lengths, the largest winning margin in modern thoroughbred racing history; world record time 2.40.8
- Sep 5 Iron monument unveiled at Stone churches, Flanders
Boxing Title Fight
Sep 6 Jack Dempsey KOs Billy Miske in 3 for heavyweight boxing title 1st radio broadcast of a prizefight
- Sep 6 US National Championship Men's Tennis, Forest Hills NY: Bill Tilden wins first of 6 straight US singles titles; beats Bill Johnston 6-1, 1-6, 7-5, 5-7, 6-3
- Sep 8 US Air Mail service begins (NYC to San Francisco)
- Sep 12 VII Summer Olympic Games close in Antwerp, Belgium
- Sep 14 The Trial of Sacco & Vanzetti: Sacco and Vanzetti indicted for murder
Wall Street Bombing
Sep 16 The "Wall Street bombing" occurs at 12:01 when a horse-drawn wagon explodes on Wall Street, New York, killing 38 and injuring 143
- Sep 17 Cards set a record of 12 consecutive hits in 4th (10) & 5th (2) innings
- Sep 17 National Football League is born in Canton, Ohio; 12 teams pay $100 each to join American Professional Football Association; renamed the NFL in 1922
- Sep 20 Foundation of the Spanish Legion.
- Sep 22 Chicago grand jury convenes to investigate charges that 8 White Sox players conspired to fix the 1919 World Series
- Sep 23 Alexander Millerand elected president of France
- Sep 23 Despite Japanese protests, China withdraws recognition of Tsarists representatives in China
- Sep 25 Vern Bradburn of Winnipeg Victorias kicks 9 singles in a game
- Sep 25 US National Championship Women's Tennis, Philadelphia CC: Molla Bjurstedt Mallory beats Marion Zinderstein 6-3, 6-1 for her 5th US singles crown
- Sep 28 8 Chicago White Sox baseball players are indicted by a grand jury, charged with fixing 1919 World Series; infamous "Black Sox scandal"
- Sep 28 Dirk Fock appointed as governor-general of Dutch East Indies
- Sep 29 Yankees slugger Babe Ruth sets then-MLB home run season record at 54 with a 9th inning shot off Dave Keefe in New York's 7-3 win at the Philadelphia A's
- Sep 29 Belgium annexes Eupen/Malmö dy
- Sep 29 Joseph Horne Company in Pittsburgh sells radios for $10
- Sep 30 Time Square Theater opens at 217 W 42nd St NYC