Most Reverend John J. O'Connor, D.D., was consecrated the Fourth Bishop of Newark on July 25, 1901 by Archbishop Corrigan. He attended Seton Hall and the North American College in Rome where he was ordained in 1877.
O'Connor's term was marked by the explosive population growth before World War I and the new America following the war. The Catholic population of the Diocese more than doubled during this era. After the war the population began to change from immigrant to American. Instead of ministering to various groups who spoke different languages, the new generation spoke English and was assimilated into the mainstream culture. The Diocese ministry changed from many distinct groups to a mainstream Catholic community.
O'Connor also saw the contribution that women made to society in both the religious life and in the raising of the family. He spoke at the first commencement of St. Elizabeth's College saying, "no degree of material or mental training can be too great for those upon whom the welfare of the home chiefly depends." Many orders of religious women did their part to help the Diocese and O'Connor at this time. The Sisters of St. Joseph made tremendous contributions by teaching the blind industrial related skills as well as how to read and write.
O'Connor also worked to advance the cause of Catholic education by the institution of CCD. This provided children who could not attend Catholic School with instruction in the faith at Sunday classes. During his term, The Catholic High School system was improved with the openings of many new schools across the area. O'Connor's long stay in the Diocese ended quietly in his home on the campus of Seton Hall on May 20, 1927.