American nurse and hospital administrator, remembered for her exceptional medical and administrative abilities and for her contributions to nursing education.

Julia Dempsey in August 1878 entered the Third Order Regular of St. Francis of the Congregation of Our Lady of Lourdes, taking the name Sister Mary Joseph. She taught school in many places over the next several years before being called to Rochester in 1889 to help staff the new St. Mary's Hospital, built by her order in the wake of a disastrous tornado. The hospital medical staff consisted of the Mayo family—William W. Mayo and his two sons, Charles H. and William J. Mayo. Sister Mary Joseph studied nursing under a local nurse and in 1890 became William J. Mayo's first surgical assistant, a post she held until 1915. In that work she displayed rare skill and judgment. In September 1892 she was also appointed superintendent of St. Mary's Hospital, a task she was to carry on for the rest of her life. During that nearly 40 years, the hospital underwent six major expansions, growing from 45 to 600 beds and in time incorporating the most modern and efficient facilities, particularly for surgery. In 1906 Sister Mary Joseph opened St. Mary's Hospital School for Nurses, which trained both sisters and laywomen. In 1915 she helped organize the Catholic Hospital Association of the United States and Canada and was chosen its first vice president. In addition to her work at St. Mary's, her remarkable administrative and medical skills contributed greatly to the success of the Mayo brothers in establishing their world-famous surgical practice and their Mayo Clinic.