[2] He attended the theological seminary at St. Mary's for four years before continuing his studies at the Pontifical North American College in Rome.

[1] Northrop was ordained to the priesthood in Rome by Patriarch Pietro de Villanova Castellacci for the Diocese of Charleston on June 25, 1865.

[2] On September 16, 1881, Northrop was appointed the second vicar apostolic of North Carolina and titular bishop of Rosalia by Pope Leo XIII.

[3] He received his episcopal consecration on January 8, 1882, at the Baltimore Cathedral from Cardinal James Gibbons, with Bishops John Keane and Thomas Becker serving as co-consecrators.

[3] In addition to his duties as vicar apostolic, Northrup was named the fourth bishop of the Diocese of Charleston on January 27, 1883 by Leo XIII.