Congress created the Montana Territory out of what had been at various times a component of the Oregon, Washington, Nebraska, Dakota, and Idaho Territories.
President Benjamin Harrison signed the formal proclamation admitting Montana as the 41st state in the Union.
Republicans Wilbur F. Sanders and Thomas C. Power, both of Helena, took the oath of office as Montana's first United States senators following a hotly contested election in January. Because both houses of the Montana legislature were divided between Republicans and Democrats, two sets of senators-elect presented their credentials. On April 16, the Senate voted 32 to 26 to seat the Republicans.
William A. Clark of Butte, a wealthy "Copper King" of Montana, resigned his Senate seat following an investigation of bribery charges that led to a unanimous report by the Committee on Privileges and Elections declaring Clark was not entitled to his seat. In January 1901, the state legislature again elected Clark, who this time was seated and served until 1907.
Senator Thomas H. Carter of Helena became chairman of the Committee on Irrigation and Reclamation of Arid Lands, serving until 1911.
Senator Joseph M. Dixon of Missoula was appointed national campaign chairman for the Progressive "Bull Moose" Party that nominated Theodore Roosevelt as its candidate for president.
Senator Henry Lee Myers of Hamilton became chairman of the Committee on Irrigation and Reclamation of Arid Lands serving until 1915.
Senator Thomas J. Walsh of Helena became chairman of the Committee on Mines and Mining, serving until 1919.
Senator Thomas J. Walsh opened the investigation into the Teapot Dome oil leases that led to the resignations of Attorney General Harry Daugherty and Interior Secretary Albert Fall. Six years later, Fall became the first former cabinet secretary to be convicted of bribery and corruption.
At the request of Senator Burton K. Wheeler of Butte, the Senate passed a resolution appointing a special committee to investigate his indictment by a federal grand jury in Montana on charges of having been paid to represent clients in cases where the U.S. government was an interested party. Wheeler asserted that the indictment was an attempt to interfere with his investigation into former attorney general Harry Daugherty's failure to prosecute government officials implicated in the Teapot Dome oil-leasing scandal. The committee reported that it found the charges groundless and on May 23, 1924, the Senate voted 56 to 5 to exonerate Wheeler.
Senator Burton K. Wheeler accepted the nomination for vice president of the United States on the Progressive Party ticket headed by Wisconsin senator Robert M. La Follette; they lost in November to the Republican incumbent president Calvin Coolidge.
The wealthy former senator William A. Clark died at his mansion in New York City, leaving his extensive collection of European art, including almost 200 paintings, sculptures, tapestries, rugs, antiquities, stained glass windows, and a Louis XVI-era salon, to the Corcoran Gallery in Washington.
Senator Thomas J. Walsh was elected chairman of the Democratic National Convention in Chicago that nominated Franklin D. Roosevelt as its presidential candidate.
Senator Burton K. Wheeler became chairman of the Committee on Indian Affairs, serving until 1935. He then became chairman of the Committee on Interstate Commerce (now the Committee on Commerce, Science, and Transportation), serving until 1947.
Senator Burton K. Wheeler led the opposition to President Franklin D. Roosevelt's proposal to expand (or "pack") the U.S. Supreme Court. Breaking with the New Deal, Wheeler then became an isolationist opponent of Roosevelt's foreign policies and a leader of the America First Committee.
Senator James E. Murray of Butte became chairman of the Committee on Education and Labor (now the Committee on Health, Education, Labor, and Pensions), serving until 1947. In 1951 he became chairman of the Committee on Labor and Public Welfare, which also eventually became the Committee on Health, Education, Labor, and Pensions.
Senator Mike Mansfield was elected the Democratic floor leader and Senate majority leader. He held that post for a record 16 years, always in the majority, until his retirement from the Senate in 1977.
To assist the elderly Senate President pro tempore, Carl Hayden during the long filibuster against the Civil Rights Act of 1964, Senator Lee Metcalf of Helena was elected permanent acting president pro tempore, a position he retained until his death in 1978, and which no other senator has held.