January 8 - President William McKinley places Alaska under military rule.
January 16 - The United States Senate accepts the Anglo-German treaty of 1899 in which the United Kingdom renounces its claims to the Samoan islands.
January 29 - The American League is organized in Philadelphia, Pennsylvania with 8 founding teams.
January 31 - Datu Muhammad Salleh is assassinated in Kampung Teboh, Tambuan, ending the Mat Salleh Rebellion
February 3 - Gubernatorial candidate William Goebel is assassinated in Frankfort, Kentucky.
February 5 - The United States and the United Kingdom sign treaty for Panama Canal
February 6 - The international arbitration court at The Hague is created when the Netherlands' Senate ratifies an 1899 peace conference decree. wow
February 8 - British troops are defeated by Boers at Ladysmith, South Africa.
February 9 - Davis Cup competition is established.
February 14 - Russia responds to international pressure to free Finland by tightening imperial control over the country.
February 14 - Second Boer War: In South Africa, 20,000 British troops invade the Orange Free State.
February 23 - In South Africa, the Boers and British troops fight in the Battle of Hart's Hill.
February 27 - Second Boer War: In South Africa, British military leaders receive an unconditional notice of surrender from Boer General Piet Cronje at the Battle of Paardeberg.
February 27 - The British Labour Party is founded.
February 28 - The Second Boer War: The 118-day "Siege of Ladysmith" is lifted.
March 11 - Second Boer War: Boer leader Paul Kruger's peace overtures are rejected by Prime Minister of the United Kingdom Lord Salisbury.
March 13 - Second Boer War: British forces occupy Bloemfontein, Orange Free State.
March 13 - In France the length of the workday for women and children is limited to 11 hours by law.
March 14 - The Gold Standard Act is ratified, placing United States currency on the gold standard.
March 16 - Sir Arthur Evans purchases the land around the ruins of Knossos, the largest Bronze Age archaeological site on Crete.
March 24 - New York City Mayor Robert Anderson Van Wyck breaks ground for a new underground "Rapid Transit Railroad" that would link Manhattan and Brooklyn.
April 2 - The Foraker Act passes through Congress, giving Puerto Ricans limited self-rule.
April 30 - Hawaii becomes a territory of the United States, with Sanford B. Dole as governor.
April 30 - Casey Jones dies in a train wreck in Vaughn, Mississippi, while trying to make up time on the Cannonball Express.
May 1 - The Scofield mine disaster kills 200 in Scofield, Utah in what is to date the fifth-worst mining accident in United States history.
May 2 - Oscar II, King of Sweden, declares support for the United Kingdom at the time of the Second Boer War.
May 17 - Second Boer War: British troops relieve Mafeking.
May 18 - The United Kingdom proclaims a protectorate over Tonga.
May 23 - American Civil War: Sergeant William Harvey Carney becomes the first African American to be awarded the Medal of Honor, for his heroism in the Assault on the Battery Wagner.
May 24 - Second Boer War: The United Kingdom annexes the Orange Free State.
June 5 - Second Boer War: British soldiers take Pretoria.
June 14 - Hawaii becomes a United States territory.
June 14 - The Reichstag approves a second law that allows the expansion of the German navy.
June 18 - Empress Dowager Longyu of China orders all foreigners killed, including foreign diplomats and their families.
July 2 - First zeppelin flight takes place on Lake Constance near Friedrichshafen, Germany.
July 9 - Queen Victoria gives royal assent to an Act creating the Commonwealth of Australia thus uniting separate colonies on the continent under one federal government.
July 29 - In Italy, King Umberto I of Italy is assassinated by Italian-born anarchist Gaetano Bresci.
August 3 - Firestone Tire & Rubber Company founded.
August 14 - A joint European-Japanese-United States force (Eight-Nation Alliance) occupies Beijing, in a campaign to end the bloody Boxer Rebellion in China.
August 20 - Japan's primary school law is amended to provide for four years of mandatory schooling.
September 8 - Galveston Hurricane of 1900: a powerful hurricane hits Galveston, Texas killing about 8,000 people.
September 13 - Filipino resistance fighters defeat a small American column in the Battle of Pulang Lupa, during the Philippine-American War.
September 17 - Philippine-American War: Filipinos under Juan Cailles defeat Americans under Colonel Benjamin F. Cheatham at Mabitac.
September 19 - Butch Cassidy and the Sundance Kid commit their first robbery together.
October 25 - The United Kingdom annexes the Transvaal.
November 7 - Battle of Leliefontein, a battle during which the Royal Canadian Dragoons win three Victoria Crosses.
December 7 - Max Planck, in his house at Grunewald, on the outskirts of Berlin, discovers the law of black body emission.
December 14 - Quantum Mechanics: Max Planck presents a theoretical derivation of his black-body radiation law.
December 18 - The Upper Ferntree Gully to Gembrook Narrow-gauge (2 ft 6 in or 762 mm) Railway (now the Puffing Billy Railway) in Victoria, Australia is opened for traffic.
