Maguire was appointed assistant chancellor of the archdiocese in 1940, vice-chancellor in 1945 and chancellor in 1947. The Vatican elevated Maguire to the rank of domestic prelate in 1948. In 1953, Archbishop Francis Spellman named Maguire as vicar general of the archdiocese, a post he held until 1980.[5][2]
Maguire was also an outspoken supporter of ecumenism and frequently participated in joint services with clergymen from other faiths.[5] He also took a special interest in the Hispanic Catholic community, learning Spanish and often traveling to Puerto Rico.[2]
Coadjutor Archbishop of New York
On September 15, 1965, Maguire was named coadjutor archbishop of New York and titular archbishop of Tabalta by Pope Paul VI.[4] His appointment placed New York in the unique situation of having two archbishops at the same time. A coadjutor is usually named when the ordinary of an archdiocese or diocese is ill or close to retirement, or when a diocese is particularly large; the 76-year-old Spellman had recently undergone prostate surgery.[3] However, unlike most coadjutor bishops, Maguire did not possess the automatic right of succession.[6]
Following Spellman's death in December 1967, Maguire was elected by the archdiocesan board of consultors to serve as apostolic administrator of New York until the pope named a new archbishop.[7] In the interim, he was mentioned as a top candidate to fill the vacant post, but Paul VI ultimately appointed Auxiliary Bishop Terence Cooke as archbishop in March 1968.[5]
Later life and death
After reaching the mandatory retirement age of 75, Maguire resigned as coadjutor archbishop and vicar general on January 8, 1980.[4] During his retirement, Maguire resided at the rectory at St. Patrick's Cathedral.[5]
Maguire died on July 6, 1989, at St. Vincent's Hospital in Manhattan at age 84.[4] Upon his death, Cardinal John O'Connor said, "For myself, Archbishop Maguire was the linchpin which linked the archdiocese of yesterday with the archdiocese of today." Maguire is interred near the deceased archbishops of New York in the crypt beneath the main altar of St. Patrick's Cathedral.