- Sep 1 Philadelphia Phillies outfielder Vince DiMaggio smashes his 4th grand slam of season, tying NL record, in an 8-3 win v Boston Braves
Surrender of Japan
Sep 2 V-J Day, formal surrender of Japan signed aboard USS Missouri marks the end of World War II (US date, 3rd September in Japan)
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Event of Interest
Sep 2 Ho Chi Minh declares Vietnam independent from France (National Day)

Ho Chi Minh
- Sep 2 V-J Day, formal surrender of Japan aboard USS Missouri marks the end of World War II (Japanese date, 1st September in US)
- Sep 3 World War II: Japanese forces in the Philippines surrender to the Allies
- Sep 3 US National Championship Men's Tennis, Forest Hills: American Frank Parker successfully defends title; beats William Talbert 14-12, 6-1, 6-2
- Sep 3 US Women's National Tennis Championship, Forest Hills: Sarah Palfrey Cooke wins second US title; beats Pauline Betz Addie 3-6, 8-6, 6-4
- Sep 4 American chess grandmaster Reuben Fine wins 4 simultaneous rapid (10 seconds per move) games blindfolded in New York City
- Sep 4 US regains possession of Wake Island from Japan
- Sep 6 A's catcher Greek George punches umpire Joe Rue gets suspended
- Sep 7 Japanese at Rioekioe-islands surrender
- Sep 7 Joe Kuhel hits inside-the-park HR, only HR hit by a Senator all season at Washington's Griffith Stadium
- Sep 8 US invades Japanese-held Korea
- Sep 9 Japanese in South Korea, Taiwan, China, Indochina surrender to Allies
Event of Interest
Sep 9 Jimmie Foxx hits his 534th & final HR

Jimmie Foxx
- Sep 9 Philadelphia A's Dick Fowler no-hits St Louis Brown, 1-0
Event of Interest
Sep 9 1st "bug" in a computer program discovered by Grace Hopper, a moth was removed with tweezers from a relay & taped into the log

Grace Hopper
- Sep 10 KLS-AM in Oakland Ca changes call letters to KWBR (now KDIA)
Event of Interest
Sep 10 Vidkun Quisling sentenced to death for collaborating with Nazis

Vidkun Quisling
Miracle Mike!
Sep 10 Mike the Headless Chicken is decapitated in Fruita, Colorado; he survives for another 18 months before choking to death.
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Event of Interest
Sep 11 Hideki Tojo, Japanese Prime Minister during most of World War II, attempts suicide rather than face war crimes tribunal but fails - later he is hanged

Hideki Tojo
- Sep 11 Physician Willem J Kolff performs the first successful kidney dialysis using his artificial kidney machine, the Netherlands
- Sep 15 A hurricane in southern Florida and the Bahamas destroys 366 planes and 25 blimps at NAS Richmond.
- Sep 16 Barometric pressure at 856 mb (25.55") off Okinawa (record low)
- Sep 18 1000 whites walk out of Gary, Indiana, schools to protest integration
Event of Interest
Sep 19 Kim Il-sung arrives in harbor of Wonsan, Korea

Kim Il-sung
Event of Interest
Sep 19 Lord Haw Haw (William Joyce) sentenced to death in London

William Joyce
MacArthur Meets Hirohito
Sep 27 US General and head of the Allied occupation of Japan, Douglas MacArthur, meets Emperor Hirohito in Tokyo for the first time
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Film Release
Sep 28 "Mildred Price" starring Joan Crawford opens at Strand

Joan Crawford
Event of Interest
Sep 30 Detroit's future Baseball Hall of Fame first baseman Hank Greenberg smacks an AL pennant-winning grand slam on the final day of the season as the Tigers beat St. Louis Browns, 6-3

Hank Greenberg
- Sep 30 Bourne End rail crash, Hertfordshire, England killed 43