Bishop David W. Bacon from Brooklyn, NY was ordained as the first Bishop of Portland on May 31, 1855 in St. Dominic's Church, the first Catholic Church in Portland, which became the pro-cathedral. At that time the Diocese comprised both Maine and New Hampshire.

One of Bishop Bacon's first major projects was to acquire land for a cathedral site--the property where the Cathedral of the Immaculate Conception today is situated. In May, 1856 he dedicated the cornerstone for the Chapel and in December of that same year he dedicated the completed Chapel. Construction of the Cathedral began on May 31, 1866, but was totally destroyed the following July in Portland's devastating fire. Several other church properties were also destroyed, in addition to his own residence. Bishop Bacon had chosen as his motto, "Courage and Hope," and it was with this spirit that he was able to move forward to rebuild and purchase other properties. The Chapel was the first project undertaken, followed soon after by the purchase of a building on Free Street which became the Episcopal residence until the present one was completed in 1869 directly behind the soon-to-be-built Cathedral.

In order to raise funds to rebuild the Cathedral, Bishop Bacon made a lengthy tour, including Boston, New York and Canada. He returned to Portland for the dedication of the Chapel in December 1867. Work on the Cathedral was started in the spring of 1868 under the direction of the famed New York architect, Patrick Keeley. Bishop Bacon had been his pastor at the Assumption Church in Brooklyn.

The dedication of the Cathedral took place on September 8, 1869, attended by 2,000 ticket holders and celebrated by Bishop John Joseph Williams of Boston. He and Bishop Bacon had several sub-deacons serving them. Numerous priests were also in attendance. The newspapers of the day described in considerable detail the ceremony as well as the magnificence of the Cathedral itself. However, this glorious day in the history of the new Portland Diocese was not to end peacefully. Bad weather had been threatening all day, and toward evening a "terrible gale" arose which broke the Cathedral's steeple. No one was hurt in the incident, for which Bishop Bacon offered a prayer of thanksgiving. The very next day workmen were on the site constructing a stronger steeple. By the end of October it was completed and the 13-foot cross was once again raised into place. It remains there to this day, rising 203'4" over the Cathedral, the highest point in Portland.

Work also continued on the interior of the Cathedral, thus assuring that its magnificence would equal that of the exterior.

Following a trip to Rome in late 1874, Bishop Bacon became seriously ill and died in New York on November 4 of that year. His funeral was held in the Cathedral on November 5.

Bishop Bacon's magnificent legacy to his church was the purchase of several buildings and properties to house churches, schools and convents. He accomplished this during a time of considerable prejudice against Catholics when some churches throughout Maine were actually destroyed and had to be rebuilt. At the time of his death and despite these prejudices, the Catholic population had grown to 70,000 and the Diocese had 63 churches, 22 schools and convents and 52 priests.

In the Family Record in 1873, Bishop Bacon had written that he was the last surviving member of his family and requested that his family members be buried in the vault of his Episcopal chapel and that his remains be buried in the Cathedral crypt, and not be removed from there by any of his successors. A later Bishop, Louis S. Walsh (1906-1924), is also buried in the crypt.