January 3 – Benito Mussolini makes a pivotal speech in the Italian Chamber of Deputies. Historians now trace this speech to the beginning of Mussolini’s dictatorship.
January 27–February 1 – The 1925 serum run to Nome (the “Great Race of Mercy”) relays diphtheria antitoxin by dog sled across the U.S. territory of Alaska, to combat an epidemic.
February 21 – The cover date of the very first issue of The New Yorker.
March 4 – Calvin Coolidge is sworn in for a full term as President of the United States, in the first inauguration to be broadcast on radio.
March 18 – The Tri-State Tornado, the deadliest in U.S. history, rampages through Missouri, Illinois, and Indiana, killing 695 people and injuring 2,027
April – The Exposition Internationale des Arts Décoratifs et Industriels Modernes opens in Paris, giving a name to the Art Deco style.
April 10 – F. Scott Fitzgerald publishes The Great Gatsby
April 20 – Iranian forces of Rezā Shāh occupies Ahvaz and arrests Sheikh Khaz’al.
April 28 – Presenting the budget, Chancellor of the Exchequer Winston Churchill announces Britain’s return to the gold standard.
May 5 – Dayton, Tennessee, biology teacher John T. Scopes is arrested for teaching Charles Darwin’s Theory of Evolution.
June 13 – Charles Francis Jenkins achieves the first synchronized transmission of pictures and sound, using 48 lines and a mechanical system in ”the first public demonstration of radiovision”
July 18 – Adolf Hitler publishes Volume 1 of his personal manifesto Mein Kampf.
July 21 – In Dayton, Tennessee, high school biology teacher John T. Scopes is found guilty of teaching evolution in class and fined $100.
August 8 – The Ku Klux Klan demonstrates its popularity by holding a parade with an estimated 30,000-35,000 marchers in Washington DC.
October 1 – Mount Rushmore National Memorial is dedicated in South Dakota.
October 2 – In London, John Logie Baird successfully transmits the first television pictures with a greyscale image.
October 5–16 – The Locarno Treaties are negotiated.
November 14 – The first Surrealist art exhibition opens in Paris.
November 26 – Prajadhipok (Rama VII) is crowned as King of Siam.
November 28 – The weekly country music-variety radio program Grand Ole Opry is first broadcast on WSM radio in Nashville, Tennessee, as the ”WSM Barn Dance”.