After the sale of the colony to the United States in 1803, the Holy See appointed the Rev. Louis Dobourg, S.S., as the Apostolic Administrator of the diocese.
He was ordained to the priesthood on 23 September 1825, in the chapel of the Daughters of Charity, by Louis Dubourg, S.S., newly installed as the Bishop of Montauban, and on the following day he presided for the first time at Mass.
The Sulpicians, who settled on the Island of Montreal in 1657, possessed, beginning in 1666, a little orchard inside the fenced garden of the seminary on Notre-Dame Street.
In March 1663, Seigniorial rights to the Island of Montreal were transferred by the Société de Notre-Dame de Montréal to the Sulpicians.