St. Mary's Assumption was built by German Catholics in 1858 in Baroque-style architecture. A room behind the High Altar contains the Seelos Museum, which includes a shrine dedicated to the saint-to-be-Blessed Francis X. Seelos.
Blessed Seelos was a German-born priest who came to New Orleans in 1866 and served priestly duties to the sick during a yellow fever epidemic. He became infected by the disease and died in 1867. Many believe that blessed Francis X. Seelos performed a miracle and cured Mary Ellen Heibel from cancer after doctors said there was no hope for a recovery.
Pope John Paul II proclaimed Father Seelos Blessed in St. Peter's Square on April 9, 2000. The church was added to the National Register of Historic Places in the 1980s.