Jeanne Fontbonne entered a house of the Sisters of St. Joseph in 1778, which had just been established at Monistrol by Bishop de Gallard of Le Puy. The following year she received the habit, and soon gave evidence of unusual administrative powers. On her election six years later as superior of the community, Mother St. John, as she was now called, aided in the establishment of a hospital, and accomplished much good among the young girls of the town.
At the outbreak of the Revolution, she and her community followed Bishop de Gallard in refusing to sign the Oath of the Civil Constitution of the Clergy, resulting in the persecution of the sisters. Forced to disperse her community, the superior remained at her post till she was dragged forth by the mob and the convent taken possession of in the name of the Commune. She returned to her father's home, but not long afterwards she was torn from this refuge, to be thrown into the prison of Saint-Didier, and scheduled to be beheaded at the guillotine. One day before that scheduled execution, she was freed after the fall of Robespierre.
Unable to regain possession of her convent at Monistrol, she returned to her father's house. Twelve years later (1807), Mother St. John was called to Saint-Etienne as head of a small community of young girls and members of dispersed congregations, who at the suggestion of Cardinal Fesch, Archbishop of Lyons, were now established as a house of the Sisters of St. Joseph. She restored the asylum at Monistrol, repurchased and reopened the former convent, and in 1812, the congregation was reborn.
In 1816 Mother St. John was appointed superior general of the Sisters of St. Joseph, and summoned to Lyons to found a general mother-house and novitiate, which she accomplished after many difficult years of labor. During the remainder of her life she was busied in perfecting the affiliation of the scattered houses of the congregation, and established over 200 new communities. An object of her special attention was the little band which she sent to the United States in 1836, and with which she kept in constant correspondence, making every sacrifice to provide them with the necessities.