- Sep 1 Kenchoji Rinzai temple in Kamakur Japan, heavily damaged by earthquake
- Sep 2 Rudolf Friml and Herbert Stothart's "Rose Marie" opens to rave reviews in NYC
- Sep 2 44th U.S. Men's National Championship: Bill Tilden beats Bill Johnston (6-1, 9-7, 6-2)
- Sep 3 Civil war breaks out in China (Gen Tsi moves to Shanghai)
- Sep 3 L Stallings & M Anderson's "What Price Glory?" premieres in NYC
Assassination Attempt
Sep 6 Assassination attempt on Benito Mussolini fails
Benito Mussolini
- Sep 6 Charles Paddock captures 100 & 200 yd AAU national senior outdoor track & field championships
- Sep 8 Alexandra Kollontai of Russia becomes 1st woman ambassador
- Sep 9 Hanapepe Massacre occurs on Kauai, Hawaii.
- Sep 10 Giants rip Braves 22-1, Frisch goes 6-for-6 before grounding out
- Sep 10 Leopold and Loeb found guilty of the murder of Robert Franks in Chicago in the "the crime of the century"
- Sep 13 19th Davis Cup: USA beats Australia in Philadelphia (5-0)
Event of Interest
Sep 14 Walter Johnson selected as the American League MVP
Walter Johnson
Golf Major
Sep 20 7th PGA Championship: Walter Hagen wins at French Lick CC, Indiana
Walter Hagen
- Sep 20 Carl Mays is 1st pitcher to win 20 games seasons for 3 different teams
- Sep 20 Cub's Grover Cleveland Alexander beats NY Giants to win 300th game
- Sep 24 Boston, Massachusetts, opens its airport
- Sep 25 Malcolm Campbell sets world auto speed record at 146.16 MPH
- Sep 27 Giants clinch their 4th straight pennant, beating Phils 5-1
- Sep 28 2 US Army planes end around-world flight, Seattle to Seattle, 57 stops
- Sep 28 French government names Gen Serrail governor-general of Syria
- Sep 28 General Plutarco Calles elected president of Mexico
- Sep 29 Santo Domingo joins League of Nations
- Sep 29 Senators clinch pennant, finishing 2 games in front of Yankees
- Sep 30 Allies stop checking on German navy