Series consists of records related to Mullock's life as a priest and Bishop, including his ecclesiastical appointments; pastoral and circular letters; documentation related to the establishment of St. Patrick's Church (1864) and the Roman Catholic Board of Education (1847, 1850-1) and correspondence with colleagues in Newfoundland, Nova Scotia, Ireland and Rome. Series also includes correspondence relating to secular topics, including the establishment of telegraph cable facilities in Newfoundland, French Treaties related to the fisheries; the British Garrison in St. John's and jurisdictional issues related to Anticosti and Blanc Sablon.
The files are arranged thematically, except in the case of correspondence, which is organized chronologically.