The diocese comprises the northern half of the Province of New Brunswick, including the counties of Gloucester, Madawaska, Northumberland, Restigouche, Victoria, and the part of Kent north of the Richibucto River.

This territory formerly belonged to the Diocese of St. John, itself originally a portion of the Archdiocese of Quebec.

On his arrival at Chatham, Bishop Rogers found only seven priests to attend an immense stretch of country.

The Catholic population in 1908 numbered about 66,000; a large percentage of which is French Acadian by descent and language.

The Trappist Fathers and the Trappistine Sisters, expelled from France, have opened monasteries in the parish of Rogersville.