Two major turning points in her career were the deaths of her husband and children during a yellow fever epidemic in Tennessee in 1867 and the loss of all her property in the Great Chicago Fire of 1871. Forced to support herself, she became involved in the labor movement, joined the Knights of Labor, a predecessor to the Industrial Workers of the World (IWW), or "Wobblies," which she helped to found in 1905. She was active as an organizer and educator in strikes throughout the country, and was particularly involved with the United Mine Workers (UMW) and the Socialist Party of America. As a union organizer, she became prominent for organizing the wives and children of striking workers in demonstrations on their behalf. In 1903, she organized children working in mills and mines in the "Children's Crusade"---a march from Kensington[?], Pennsylvania to Oyster Bay[?], [[New York, home of President Theodore Roosevelt, with banners demanding "We want time to play!" and "We want to go to school!" Though the President refused to meet with the marchers, the incident brought the issue of child labor to the forefront of the public agenda.
In 1913, during the Paint Creek-Cabin Creek strike in West Virginia, Mother Jones was arrested and convicted with other union organizers of conspiring to commit murder, after organizing another children's march. Already eighty-three years old, her arrest raised an uproar and she was soon released from prison, after the Senate ordering an investigation into the conditions in the coal mines. A few months later she was in Colorado, helping to organize the coal miners there. Once again she was arrested, and after serving some time in prison, deported, in the months leading up to the Ludlow Massacre.
Mother Jones remained a union organizer for the UMW affairs into her nineties, and continued to speak on union affairs almost until her hundredth birthday. Soon after her official retirement, at the age of ninety-five, she released her own account of her experiences in the labor movement as The Autobiography of Mother Jones (1925).
These days, many people know her mostly because of the American magazine Mother Jones, which advocates many of the social views that Mother Jones espoused.