John Mitchell was born in 1870 in Braidwood, Illinois, a second generation Irish immigrant. He became an orphan when he was only six years old, and began working at that age to support his family. He worked in the coal mines his whole life. When he was nineteen years old, he joined the Knights of Labor in 1885 and was a founding member of the United Mine Workers of America in 1890. He was elected District 12 secretary-treasurer in 1895. He was made an international union organizer in 1897 and worked alongside Mother Jones before being elected an international vice president the same year.
He helped organize the National Civic Federation in 1900.
He served as fourth vice president of the American Federation of Labor (AFL) from 1898 to 1900, and as second vice president from 1900 to 1914 (although he had lost the UMWA presidency in 1908).
Along with AFL Samuel Gompers and AFL secretary-treasurer Frank Morrison, he was sentenced to prison for violating a court injunction during a strike at the Buck Stove and Range Co. in St. Louis, Missouri. In a landmark case, the United States Supreme Court overturned the contempt citation in Gompers v. Buck's Stove and Range Co., finding that the court of appeals had erred in allowing the company to bring the complaint of contempt rather than the district court itself.
One of Mitchell's earliest challenges in the UMWA was to help incorporate new workers from various ethnicities into the union. There were numerous language barriers, as well as cultural biases and outright prejudice to be overcome. His success in this area helped him become vice-president in 1897, and president one year later.
Labor activity was notoriously dangerous at the time. Just before Mitchell became president, the Lattimer Massacre had seen 19 miners killed by police. But this was also a period of growth for the union: the number of members grew almost tenfold, from 34,000 to 300,000, during Mitchell's term. Mitchell engaged in contentious negotiations with mining companies, including one in which President Theodore Roosevelt had to intervene, resulting in an eight-hour workday and a minimum wage. A tributary statue of Mitchell stands on the grounds of the Lackawanna County Courthouse in Scranton, Pennsylvania, the site of the negotiations which President Roosevelt got involved in. Because of the significance of these negotiations, the statue and the Courthouse are considered National Historic Landmarks.
When his successor, Thomas Lewis, won approval of a resolution forcing UMWA members to resign from the National Civic Federation, Mitchell left the union. He continued his association with the federation for many years, as well as serving on a number of state and federal commissions.
Mitchell died in New York City in 1919.