Mary Fox was born at Edina, Missouri on April 22, 1867. She was received as a postulant at Clyde by Mother M. Anselma on July 2, 1882, at the age of fifteen. She was invested on September 14th of the same year and professed as Sister M. Clara on September 29, 1883, about a month after the death of Mother M. Anselma. She made perpetual vows on July 26, 1889. She celebrated her Golden Jubilee in 1933 and her Diamond Jubilee in 1943.. She was an aunt of Sister M. Leocadia Lager.

Presumably she graduated from St. Joseph's Academy with a teacher's diploma. For two years she taught in Maryville, then conducted classes in Church History and Christian Doctrine at the Academy. She was a dynamic person, a splendid teacher, and made her classes most interesting. Gifted with a brilliant mind and a retentive memory, she was well informed on a wide range of subjects. For a time Sister was Director of the Postulants. From September 1916 to January 1928 she was at Chewelah, Washington, in the position of Superior for some years.

Along with Sisters M. Seraphim and Innocent, Sister helped to get the Clyde printery started. After "Tabernacle & Purgatory" was finally launched as a monthly magazine, Sister M. Clara expressed the hope that the Sisters would always bear in mind that their main purpose was not to have a large subscription list or to make money, but that the magazine and booklets should do good wherever they were sent; therefore they should keep them up to a high standard and not cater to people who might wish something more sensational.

Sister had a heart ailment which brought on other complications and was bedfast in the Clyde infirmary for the last twenty-two years of her life. She attended Mass in the infirmary chapel each morning in a wheelchair, and returned in the afternoon for a period of adoration. The latter she kept most faithfully, and if unable to go to the chapel, she would keep her hour propped up in bed. Her hands were always busy with crocheting, and she prepared hundreds of Sacred Heart badges as gifts for our benefactors. Her patience and resignation in suffering, her unfailing cheerfulness, her complete trust in God's Providence, were an inspiration to all. She had great devotion to St. Therese, the Little Flower, whose spiritual doctrine was mirrored in her own. With complete abandonment to God, she saw His will in all the details of life. "God has planned our whole life," she would say, "and He can't make a mistake." With perfect trust in His goodness and mercy she believed that God would take her to heaven immediately after her death. The Sisters loved to visit her, and always came away from her bedside spiritually renewed and refreshed. Sister was able to continue her daily schedule until two days before her death. The evening of February 6th she became very ill and felt she was soon to die. Father Anselm Coppersmith (then Chaplain) gave her the anointing of the sick and holy Viaticum. After passing through a series of crises, she died peacefully the evening of February 8th, 1950, in the 83rd year of her life and the 67th of her religious profession.