She was born on April 29, 1939, in Somerville, Mass., to Ellen (McAuliffe) and John Sheehan. She graduated from Girls Catholic High School in Malden, Mass., in 1956. In 1957, Sister Mary entered the Daughters of Charity in Emmitsburg, Md. She earned her bachelor of arts in mathematics with a minor in education from St. Joseph College in Emmitsburg in 1971, and her master of science in institutional administration from University of Notre Dame in South Bend, Ind., in 1976.

After serving in New York and Maryland as teacher and principal, Sister Mary was sent to Our Lady of the Valley Church in Gloverville, S.C., for parish ministry from 1977 to 1979, before heading to Baltimore, Md., as an assistant principal. Her work took her to Pensacola and Jacksonville in Florida for hospital administration from 1983 to 1996.

After a few short-term missions, Sister Mary returned to Gloverville to serve at Our Lady of the Valley Center as director of religious education and education coordinator from 2002 to 2013. In 2015, Sister Mary was missioned to Villa St. Michael for the Ministry of Prayer, which she held until her death.

She was preceded in death by her parents and two brothers, and is survived by two sisters, two brothers, many nieces, nephews and her sisters in the Daughters of Charity community.

A Mass of Christian Burial was held March 27 in the Basilica of the National Shrine of St. Elizabeth Ann Seton in Emmitsburg, and burial followed in the Sacred Heart Cemetery on the grounds.

Donations may be made in Sister Mary Sheehan's name to the Daughters of Charity, 4330 Olive Street, St. Louis, MO 63108.