After Jones' husband and four children all died of yellow fever in 1867, and her dress shop was destroyed in the Great Chicago Fire of 1871, she became an organizer for the Knights of Labor and the United Mine Workers union. In 1902, she was called "the most dangerous woman in America" for her success in organizing mine workers and their families against the mine owners. In 1903, to protest the lax enforcement of the child labor laws in the Pennsylvania mines and silk mills, she organized a children's march from Philadelphia to the home of President Theodore Roosevelt in New York.