Mary Prudence was born Sept. 16, 1912, the daughter of William and Susan Wathen Thomas of Calvary, Ky. Her education began at St. Joseph School in Raywick where she remained through her freshman year in high school. Mary Prudence went to St. Charles School in Lebanon for her sophomore year, then attended Mount Saint Joseph Academy during her junior year. In her senior year, she entered the novitiate and completed her high school studies during her postulancy. On March 19, 1931, Mary Prudence received the Ursuline habit and the name Sister Mary DeSales.
Sister Mary DeSales was first assigned to St. Bernard Academy in Nebraska City, Neb. Her next assignment was St. Paul School in Louisville where she spent two years teaching grades three and four. In 1938, she taught at St. Edward School in Jeffersontown, Ky., for three years. Following three years off duty because of illness, in 1943 Sister went to Clementsville, Ky., for one year and St. Denis in Shively, Ky., for three years. For the next 10 years, she taught grades 1 and 2 at Good Shepherd School in Hillsboro, Mo. She returned to Kentucky and taught at Browns Valley for nine years. From there she was missioned to St. Edward in Jeffersontown from 1966 to 1979.
On July 2, 1979, while at St. Edward, Sister Mary DeSales underwent surgery at Suburban Hospital in Louisville, which revealed cancer of the liver and pancreas. Following a stroke, Sister was brought to the infirmary at Mount Saint Joseph where she lingered for five weeks. Death came to her on September 26, 1979. Father Bernard Barnes, chaplain, was the main celebrant of the funeral Mass. Other priests concelebrating with Father Barnes were Father Joseph Hamilton, pastor of St. Edward Parish in Jeffersontown, who gave the homily, and the pastors from six other parishes where Sister Mary DeSales had ministered.
Sister’s remains are buried in the convent cemetery. As a gesture of love for all that Sister Mary DeSales meant to them, the parishioners from St. Edward in Jeffersontown donated her tombstone. Among her survivors was her Ursuline sister, Sister Mary David.