She was longtime executive at the St. Joseph's Orphan Asylum in Philadelphia, and during the American Civil War she was Superioress at the Satterlee Hospital in the same city.

In 1822, ten-year-old Agnes was enrolled as a student at St. Joseph's Valley, a school run by the Sisters of Charity.

Sister Mary Gonzaga stayed at the latter order's mother house in Paris from 1855 to 1856, to work on the details of that union.

[1][6] "In her demise there passed out of this life a woman of boundless charity, whose ministrations among thousands of Union and Confederate soldiers contributed a note of beauty to the many harassing details of the war," remarked Rhode Island congressman Ambrose Kennedy in the Congressional Record in 1918.

One of her former students, poet Eleanor C. Donnelly,[1] wrote a book-length biography of Sister Mary Gonzaga in 1900, as a fundraiser for the work of the new orphanage.