Seelos, born in Bavaria, came to the United States in 1843 after joining the Redemporist Fathers. His early years as a Redemptorist were spent in New York, Baltimore, and Pittsburgh, where he assisted St. John Neumann. He went back to Baltimore in 1854, then to Cumberland, and then to Annapolis. His ministry was parish work and the formation of Redemptorist seminarians. From 1863 to 1866, he traveled about the country preaching missions. Assigned to New Orleans in 1866, he died there the following year, having contracted yellow fever from the victims to whom he had ministered.
C. Hoegerl, trans. and ed., Sincerely Seelos: The Collected Letters of Blessed Francis Xavier Seelos