There were two turning points in her life. The first, and most tragic one, was the loss of her husband George and their four children, three girls and a boy (all under the age of five) in 1867, during a yellow fever epidemic in Memphis. After that tragedy, she returned to Chicago to begin another dressmaking Business. Then, four years later, she lost her home, shop, and possessions in the Great Chicago Fire of 1871. This huge fire destroyed many homes and shops. Jones, like many others, helped rebuild the city. According to her autobiography, this led to her joining the Knights of Labor. She started organizing strikes. At first the strikes and protests were a horrific failure and usually ended with the police shooting at and killing numerous protesters. The Haymarket Riot of 1886 and the fear of anarchism and upheaval incited by union organizations resulted in the demise of the Knights of Labor. Once the Knights ceased to exist, Mary Jones became involved mainly with the United Mine Workers. She frequently led UMW strikers in picketing and encouraged striking workers to stay on strike when management brought in strike-breakers and militias. She strongly believed that "working men deserved a wage that would allow women to stay home to care for their kids." Around this time, strikes were getting better organized and started to produce greater results, such as better pay for the workers.