1. United States
1.1. 1900
1.1.1. At the Carnegie Steel Company, Slavs and Italians produce one-third of the world's total steel supply.
1.1.2. January 1900
1.1.2.1. January 1 – Hawaii asks for a delegate at the U.S. Republican National Convention.
1.1.2.2. January 2 – John Hay announces the Open Door Policy to promote trade with China.
1.1.2.3. January 2 – The first electric bus becomes operational in New York City.
1.1.2.4. January 3 – The United States Census estimates the country's population was 70 million.
1.1.2.5. January 8 – United States President William McKinley places Alaska under military rule.
1.1.2.6. January 14 – The United States Senate accepts the Anglo-German treaty of 1899, in which the United Kingdom renounces its claims to the Samoan islands.
1.1.2.7. January 17 – Brigham H. Roberts is refused a seat in the United States House of Representatives because of his polygamy.
1.1.2.8. February 1900
1.1.2.8.1. February 5 – Britain and the United States sign a treaty for the building of a Central American shipping canal through Nicaragua.
1.1.2.8.2. February 9 – Dwight F. Davis creates the Davis Cup tennis tournament.
1.1.2.8.3. March 1900
1.1.3. Milton S. Hershey introduces the milk chocolate Hershey bar.
1.2. 1901
1.2.1. January
1.2.1.1. January 3 - Census Commissioner predicts a US population of at least 300 million by 2001
1.2.1.2. January 5 – Typhoid fever breaks out in a Seattle jail, the first of two typhoid outbreaks in the USA during the year.
1.2.1.3. January 10 – In the first great Texas gusher, oil is discovered at Spindletop in Beaumont, Texas.
1.2.1.4. January 28 – Baseball's American League declares itself a Major League.
1.2.1.5. February
1.2.1.5.1. February 20 – The Hawaii Territory Legislature convenes for the first time.
1.2.1.5.2. March
1.2.2. The Intercollegiate Prohibition Association is established in Chicago.
1.3. 1902
1.3.1. January
1.3.1.1. January 1 – The first college football bowl game, the Rose Bowl between Michigan and Stanford, is held in Pasadena, California.
1.3.1.2. January 8 – A train collision in the New York Central Railroad's Park Avenue Tunnel kills 17, injures 38, and leads to increased demand for electric trains.
1.3.1.3. January 28 – The Carnegie Institution is founded in Washington, DC with a $10 million gift from Andrew Carnegie.
1.3.1.4. February
1.3.1.4.1. February 18 – U.S. President Roosevelt prosecutes the Northern Securities Company for violation of the Sherman Act.
1.3.1.4.2. February 22 – Senators Benjamin Tillman and John L. McLaurin, both of South Carolina, have a fist fight while Congress is in session.[1] Both Tillman and McLaurin are censured by the Senate on February 28.
1.3.1.4.3. February - The Yellow Fever Commission announces that the disease is carried out by mosquitoes
1.3.1.4.4. March
1.4. 1903
1.4.1. January
1.4.1.1. January 19 – The first west-east transatlantic radio broadcast is made from the United States to England (the first east-west broadcast having been made in December 1901).
1.4.1.2. January 21 – Section of Militia Affairs within the Adjutant General's office.
1.4.1.3. February
1.4.1.3.1. February 11 – The Oxnard Strike of 1903 becomes the first time in U.S. history that a labor union is formed from members of different races.
1.4.1.3.2. February 14 – Department of Commerce and Labor founded
1.4.1.3.3. February 15 – Morris and Rose Mitchom introduce the first teddy bear in America.
1.4.1.3.4. March
1.4.2. Growth of American imperialism with Panama + Cuba
1.4.3. The Lincoln–Lee Legion is established to promote the temperance movement and signing of alcohol abstinence pledges by children.