Nederlander Theatre
Sep 1 Nederlander Theatre opens at 208 W 41 St NYC, designed by William Neil Smith for theatrical impresario Walter C. Jordan, originally named the National Theatre, it was also known as the Billy Rose (1959-78), and the Trafalgar (1978-80)
- Sep 3 International Lawn Tennis Challenge, NYC, NY: Americans Watson Washburn & William Norris beat Japanese pair Ichiya Kumagae & Zenzo Shimizuto 6-2, 7-5, 4-6, 7-5 for 3-0 lead; ends 5-0
- Sep 3 KPB, Communist Party of Belgium forms
Baseball Record
Sep 5 Walter Johnson sets MLB strikeout mark at 2,287
- Sep 7 In Atlantic City, New Jersey, the first Miss America Pageant, a two-day event, is held
- Sep 8 1st Miss America crowned in Atlantic City - Margaret Gorman (16) of Washington, D.C.
- Sep 9 Guatemala, Honduras and San Salvador agree to Central American Union
- Sep 11 Nahalal, the first moshav in Israel, is settled
Alcohol Paraclitus
Sep 15 Pope Benedict XV publishes encyclical Alcohol Paraclitus
- Sep 15 WBZ-AM in Boston MA begins radio transmissions
US Men's Tennis Open
Sep 19 US National Championship Men's Tennis, Germantown CC, Philadelphia: Bill Tilden successfully defends title; beats Wallace F. Johnson 6-1, 6-3, 6-1
- Sep 21 A storage silo at a BASF fertiliser producing plant explodes in Oppau, Germany, 500—600 killed
- Sep 21 Pope Benedictus XV donates 1 million lire to feed Russians
The Music Box Opens
Sep 22 Music Box Theater opens at 239 W 45th Street, NYC; Built by theatrical producer Sam H. Harris for Irving Berlin's musical revue "The Music Box", written specifically for the venue
- Sep 22 The League of Nations accepts membership of independent Estonia, Latvia, and Lithuania
- Sep 26 Yankee Ruth hits HRs 57 & 58 to beat Indians 8-7
- Sep 27 American swimmer Johnny Weismuller sets his first 2 world records in the 100m and 150yd freestyle events the A.A.U. Nationals meet in Brighton Beach, NY
- Sep 27 MLB NY Yankees beat Cleveland Indians 21-7 at Polo Grounds, NYC
PGA Championship
Sep 28 4th PGA Championship: Walter Hagen at Inwood CC Far Rockaway NY
- Sep 29 Pirates drop doubleheader to Cards to allow idle Giants to clinch NL