Margaret Mary Casey, as she was named at her birth in 1885 in Potosi, Missouri, entered the Sisters of St. Joseph in 1913.
An elegant woman, Sister Mary Marcella was admired and respected by students, faculty, parents, and others with whom she came into contact. English was Sister's field of expertise; she taught that subject in high school before becoming Fontbonne's president in 1948. During her term in office, the college dedicated Medaille Hall and celebrated its 25th anniversary in 1948.
After her presidency, Sister Mary Marcella returned to the secondary school classroom, only retiring to Nazareth Living Center in 1964. She died there in 1966.