Lieutenant Governor of Louisiana: Jared Y. Sanders, Sr. (Democratic)
Lieutenant Governor of Massachusetts: Curtis Guild, Jr. (Republican) (until month and day unknown), Eben Sumner Draper (Republican) (starting month and day unknown)
February 28: The Jungle exposes corruption in the meatpacking industry.
January 8 – A landslide in Haverstraw, New York kills 21 people.
February 26 – Upton Sinclair publishes The Jungle, a novel depicting the life of an immigrant family in Chicago during the early 1900s.
April–June[]
April 18: 1906 San Francisco earthquake.
April 5 – The Maryland General Assembly authorises the erection of the Union Soldiers and Sailors Monument in Baltimore.
April 14 – The first service is held at African Methodist Episcopal Church in Los Angeles by W. J. Seymour, in a series later known as the Azusa Street Revival, an event which launches the Pentecostal movement in Christianity.
April 18 – The 1906 San Francisco earthquake (estimated magnitude 7.8) on the San Andreas Fault destroys much of San Francisco, California, killing at least 3,000 people, with 225,000–300,000 left homeless, and $350,000,000 in damages.
June 6 – Durham and Southern Railway operates its first revenue train, Bonsal to Durham, North Carolina.
June 8 – Theodore Roosevelt signs the Antiquities Act into law, authorizing the President to restrict the use of certain parcels of public land with historical or conservation value.
June 18 - The Lake County Times now The Times of Northwest Indiana begins publication.
June 25 – Harry K. Thaw shoots architect Stanford White at the roof garden theatre of Madison Square Garden (designed by White) in New York City.
June 28 – Osage Allotment Act allocates land to members of the Osage Nation in Oklahoma.
June 29 – Mesa Verde is declared a National Park.
June 30 – The United States Congress passes the Meat Inspection Act and Pure Food and Drug Act.
July–September[]
September 5: The first legal forward pass in an American football.
July 11 – Murder of Grace Brown, a factory worker whose killing caused a nationwide sensation.
July 14 – Gary, Indiana is founded by the United States Steel Corporation.
August 23 – Unable to control a rebellion in the newly formed Cuban Republic, President Tomás Estrada Palma requests U.S. intervention.
September 5 – Bradbury Robinson of St. Louis University throws the first legal forward pass in an American football game.
September 22 – Atlanta race riot: Race riots in Atlanta, Georgia result in 27 people killed and the Black-owned business district severely damaged.
September 24 – U.S. President Theodore Roosevelt proclaims Devils Tower, Wyoming as the nation's first National Monument.
September 26 – The first concert of the Telharmonium, the first music synthesizer, is presented at Telharmonic Hall, Broadway at 39th St., New York City.
September 30 – The first Gordon Bennett Cup in ballooning is held, starting in Paris. The winning team, piloting the balloon United States, lands in Fylingdales, Yorkshire, England, UK.
October–December[]
October 1 – The Madeira School, a private boarding school for girls, opens with 28 students attending classes in two buildings on 19th Street, just off Dupont Circle in downtown Washington, D.C.
October 11 – The San Francisco public school board sparks a United States diplomatic crisis with Japan, by ordering Japanese students to be taught in racially segregated schools.
November 9 – U.S. President Theodore Roosevelt leaves for a trip to Panama to inspect the construction progress of the Panama Canal (the first time a sitting President of the United States makes an official trip outside of the United States).
December 4 – Alpha Phi Alpha, the first inter-collegiate Greek-letterFraternity established for African Americans, is founded at Cornell University.
December 8 – The Petrified Forest, Arizona is designated a National Monument.
December 10 – U.S. President Theodore Roosevelt is awarded the Nobel Peace Prize for his role in negotiating peace in the Russo-Japanese War (1905).
Undated[]
The muffuletta sandwich is invented in New Orleans, Louisiana.