January 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.
January 23 – The Ålesund fire destroys most buildings in the town of Ålesund, Norway, leaving about 10,000 people without shelter.
January 25 – Halford Mackinder presents a paper on "The Geographical Pivot of History" to the Royal Geographical Society of London in which he formulates the Heartland Theory, originating the study of geopolitics.
February 1904
February 7 – The Great Baltimore Fire in Baltimore, Maryland, destroys over 1,500 buildings in 31 hours.
February 8–9 – Battle of Port Arthur: A surprise Japanese naval attack on Port Arthur (Lüshun) in Manchuria starts the Russo-Japanese War.
February 10 – Roger Casement publishes his account of Belgian atrocities in the Congo.
February 17 – Puccini's opera Madama Butterfly, with a background theme of Japan–United States relations, debuts at La Scala in Milan, to no great acclaim. On May 28 a revised version opens in Brescia, to huge success.
February 23 – For $10 million, the United States gains control of the Panama Canal Zone.
February 26 – The Wisconsin State Capitol, in Madison, Wisconsin, is almost entirely destroyed by fire after a gas jet ignites the newly-varnished ceiling.
March 1904
March 3 – Kaiser Wilhelm II of Germany becomes the first person to make a recording of a political document, using Thomas Edison's cylinder.
March 4 – Russo-Japanese War: Russian troops in Korea retreat toward Manchuria, followed by 100,000 Japanese troops.
March 6 – Scottish National Antarctic Expedition: Led by William Speirs Bruce, the Antarctic region of Coats Land is discovered from the Scotia.