The Joseph B. Mullin Papers document Mullin's career as a pastor and community activist. Materials in the collection also document his personal life, family, and friends. The collection includes publications and sermons written by Mullin, degrees he received including his 1957 Master's thesis, news clippings, correspondence, and photographs. Highlights of the collection include correspondence and documentation of his mission trip to the Democratic Republic of Congo, a personal memoir titled Remembering, and three folders containing correspondence between Mullin and various friends and family.