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 of cancer after doctors said there was no hope for 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.