Bishop Bacon's successor, James Augustine Healy, was appointed February 12, 1875, and consecrated as Bishop of Portland at the Cathedral of the Immaculate Conception on June 2, 1875.

James Augustine Healy became the first Black Bishop ordained in the United States. He was the son of an Irish immigrant, Michael Healy, who became a prosperous plantation-owner in Georgia, and a mulatto woman who was actually a slave.

James was educated in northern schools and later attended the newly established Holy Cross College. There he made his decision to enter the priesthood. He furthered his studies in Montreal and Paris where he was ordained in 1854 at the Cathedral of Notre Dame.

After ordination Father Healy was assigned to Bishop John Fitzpatrick's Boston Diocese. He remained there serving first at the House of the Angel Guardian, then as Chancellor of the Diocese and finally as pastor of St. James Church. When his appointment came as the second Bishop of Portland, he was forty-five years old.

As a pastor in Massachusetts, Bishop Healy had already proved himself an accomplished civil rights advocate for those who were unable to speak for themselves. Now as the new spiritual leader of Maine and New Hampshire, he had special qualifications that made him an ideal choice. On a personal level, he was half-Irish which bonded him with parishioners on Munjoy Hill, many of whom were newly arrived from Ireland. He spoke fluent French; that endeared him to the Acadians of northern Maine.

During Bishop Healy's years in Portland, his Cathedral was still a new church, requiring little renovation. This left him time for not only social justice projects but many other endeavors. The construction of the new St. Dominic's Church, the enlarging of Calvary Cemetery, the establishment of the Conference of St. Vincent de Paul for the care of the poor, the purchase of land on Little Diamond Island for the orphans' use in summer, the opening of St. Joseph's Chapel in Deering, and the establishment of Sacred Heart parish are only a few of Bishop Healy's accomplishments during his tenure.

On June 29, 1900, Bishop Healy celebrated his Silver Jubilee, but scarcely a month later, on August 5, 1900, he died. His funeral took place at the Cathedral on August 9. As he requested, burial was at Calvary Cemetery. A large Celtic cross marks his grave.