1904January 1904 January 7 – The distress signal CQD is established, only to be replaced 2 years later by SOS. January 8 – The Blackstone Library is dedicated, marking the beginning of the Chicago Public Library system. January 12 – The Herero Wars in German South West Africa begin. January 17 – Anton Chekhov's last play, The Cherry Orchard («Вишнëвый сад», Vishnevyi sad), opens at the Moscow Art Theatre directed by Constantin Stanislavski, 6 month's before the author's death.
1942The Uppsala Conflict Data Program project estimates this to be the deadliest year in human history in these terms of conflict deaths, placing the death toll at 4.62 million. However, the Correlates of War estimates that the prior year, 1941, was the deadliest such year. Death toll estimates for both 1941 and 1942 range from 2.28 to 7.71 million each. Below, the events of World War II have the "WWII" prefix.
1921January 1921 January 2 The Association football club Cruzeiro Esporte Clube, from Belo Horizonte, is founded as the multi-sports club Palestra Italia by Italian expatriates in Brazil. The Spanish liner Santa Isabel breaks in two and sinks off Villa Garcia, Mexico, with the loss of 244 of the 300 people on board. January 16 – The Marxist Left in Slovakia and the Transcarpathian Ukraine holds its founding congress in Ľubochňa. January 17 – The first recorded public performance of the illusion of "sawing a woman in half" is given by English stage magician P.
1901January 1901 January 1 The British colonies of New South Wales, Queensland, South Australia, Tasmania, Victoria and Western Australia federate as the Commonwealth of Australia; Edmund Barton becomes the first Prime Minister of Australia. Nigeria becomes a British protectorate. January 9 – Lord Kitchener reports that Christiaan de Wet has shot one of the "peace" envoys, and flogged two more, who had gone to his commando to ask the Burgher citizens of South Africa to halt fighting.
1902January 1902 January 1 The Nurses Registration Act 1901 comes into effect in New Zealand, making it the first country in the world to require state registration of nurses. On January 10, Ellen Dougherty becomes the world's first registered nurse. Nathan Stubblefield demonstrates his wireless telephone device in the U.S. state of Kentucky. January 8 – A train collision in the New York Central Railroad's Park Avenue Tunnel kills 17 people, injures 38, and leads to increased demand for electric trains and the banning of steam locomotives in New York City.
1926January 1926 January 3 – Theodoros Pangalos declares himself dictator in Greece. January 8 Abdul-Aziz ibn Saud is crowned King of Hejaz. Crown Prince Nguyễn Phúc Vĩnh Thuy ascends the throne, the last monarch of Vietnam. January 12 – Freeman Gosden and Charles Correll premiere their radio program Sam 'n' Henry, in which the two white performers portray two black characters from Harlem looking to strike it rich in the big city (it is a precursor to Gosden and Correll's more popular later program, Amos 'n' Andy).
1915Below, the events of World War I have the "WWI" prefix. January 1915 January – British physicist Sir Joseph Larmor publishes his observations on "The Influence of Local Atmospheric Cooling on Astronomical Refraction". January 1 WWI: British Royal Navy battleship HMS Formidable is sunk off Lyme Regis, Dorset, England, by an Imperial German Navy U-boat, with the loss of 547 crew. Battle of Broken Hill: A train ambush near Broken Hill, Australia, is carried out by two men (claiming to be in support of the Ottoman Empire) who are killed, together with four civilians.
1928January 1928 January – British bacteriologist Frederick Griffith reports the results of Griffith's experiment, indirectly proving the existence of DNA. January 1 – Eastern Bloc emigration and defection: Boris Bazhanov, Joseph Stalin's personal secretary, crosses the border to Iran to defect from the Soviet Union. January 17 – The OGPU arrests Leon Trotsky in Moscow; he assumes a status of passive resistance and is exiled with his family. January 26 – The volcanic island Anak Krakatau appears.
1916Below, the events of the First World War have the "WWI" prefix. January 1916 January 1 – The British Royal Army Medical Corps carries out the first successful blood transfusion, using blood that had been stored and cooled. January 9 – WWI: Gallipoli Campaign: The last British troops are evacuated from Gallipoli, as the Ottoman Empire prevails over a joint British and French operation to capture Constantinople. January 10 – WWI: Erzurum Offensive: Russia defeats the Ottoman Empire.
1929This year marked the end of a period known in American history as the Roaring Twenties after the Wall Street Crash of 1929 ushered in a worldwide Great Depression. In the Americas, an agreement was brokered to end the Cristero War, a Catholic counter-revolution in Mexico. The Judicial Committee of the Privy Council, a British high court, ruled that Canadian women are persons in the Edwards v. Canada (Attorney General) case. The 1st Academy Awards for film were held in Los Angeles, while the Museum of Modern Art opened in New York City.