Bishop Plessis was the first to introduce Christianity into the vast territory of Red River, and founded religious and educational institutions in Upper Canada and the provinces along the Gulf of St. Lawrence. In 1815 he had paid an extended visit to all the maritime colonies. His great work was the organization of his church in Canada. In 1818 he was nominated Archbishop of Quebec, and the rest of British America was formed into four suffragan sees. In the legislative council he was an ardent defender of the religious and civil rights of his co-religionists, and in 1822.