Kearns was born in 1862 in Oxford County, Ontario, Canada, to Margaret
Maher and Thomas Kearns. He moved with his Irish immigrant parents to a
farm in Nebraska and there obtained a grammar-school education. The
development of mining in the West drew him in 1883 to Park City, Utah,
where he worked, prospected, and developed with others the Silver King
mine that made him a millionaire. He married Jennie Judge, with whom he
had three children. Elected alderman in Park City, he was also a
delegate to the 1895 state constitutional convention where he advocated
an eight-hour work day.
Democratic majority in the 1899 legislature had failed to elect a U.S.
senator, leaving the seat vacant for two years. In late 1900 Kearns
announced his candidacy and was elected the following year by a
Republican-controlled legislature. Some accused LDS Church President
Lorenzo Snow of engineering the election of Kearns, a Catholic.
Well-informed on mining law, Kearns also won recognition in the Senate
for his support of Theodore Roosevelt's conservation/irrigation
programs. He worked to secure regimental post status for Fort Douglas and for opening the Uintah Indian Reservation to settlement. When he
failed to receive support for reelection, he bitterly denounced the
power of the Mormon Church in a Senate farewell speech in 1905.