The Vicariate Apostolic of Pontiac was created by a decree dated July 11, 1882, by Pope Leo XIII.

The Vicariate comprised the County of Pontiac, the County of Renfrew, the northern townships of the County of Frontenac, Addington and Hastings, sixteen townships in the County of Haliburton, and a part of Haliburton, as well as all the territory included between the height of land, on the south, the Hudson Bay, James Bay, and the Great Whale River, as far as Lake Apiokacumish on the north, the 91st degree of longitude on the west and the 72nd degree on the east.

Narcisse Z. Lorrain, nominated on July 14, was consecrated as Bishop of the Vicariate Apostolic of Pontiac on September 21, 1882.

Diocese of Pembroke (Since 1898)

Sixteen years later, on May 4, 1898, the Vicariate Apostolic of Pontiac was raised to the Diocese of Pembroke. Once again, Pope Leo XIII named Narcisse Z. Lorrain as the first Bishop of this new diocese, on May 6, 1898.100th Anniversary logo 1998, with a silhouette of the Cathedral and a map of the Diocese (On the map, the Ottawa River looks like the Spirit descending as a dove.)

The change meant that the diocese was no longer missionary in character but was now considered to be a sufficiently organized territory. The limits of the new diocese remained the same except for one exchange—the mission of Long Lake, situated north of Lake Superior would fall under the jurisdiction of the Diocese of Peterborough, while the Lake Timagami mission, situated west of Lake Témiskaming, would become the responsibility of the Diocese of Pembroke.

At that time, the diocese contained 33 churches, 37 chapels, 4 convents, 3 hospitals, 24 parishes, 33 missions, 36 priests and a Catholic population of about 40,000.

On September 21, 1908, there was a further change, a reduction in the Diocese of Pembroke, when the Vicariate Apostolic of Témiskaming was formed. Finally, a few minor changes, for the sake of convenience, were agreed upon by the bishops of Pembroke, Peterborough and Sault Ste. Marie; these changes were ratified by the Holy See on October 17, 1937.

Foundation of the Diocese
Vicariate Apostolic: July 11, 1882
Erected as a Diocese: May 4, 1898