His whole time was henceforth spent in genealogical research compilation based largely on in-situ consultation of catholic parish registers throughout Quebec, the Maritime provinces, Ontario, and the old French settlements in the United States.

As the result of his labours he published (1871–90) his Dictionnaire généalogique des familles canadiennes françaises depuis les origines de la colonie jusqu'à nos jours, comprising seven large double column volumes of over six hundred pages: a colossal undertaking, fit for a numerous body of collaborators, which he achieved alone.

Every French Canadian by completing from contemporary registers the information supplied by this dictionary can proudly trace back his genealogy to his ancestors from old France.

A plaque marks the site of the house in which he lived in the Lower Town area of Ottawa not far from the National Art Gallery and the Byward Market.

[2] Tanguay's work has been supplemented by the research and publications of others, including by Leboeuf, as above, and Abbé Archange Godbout's Origine des familles canadiennes-françaises, but was not supplanted until a century later.

[7][8] In 2002, Jetté's PRDH colleague Bertrand Desjardins made available the Gaëtan Morin Éditeur CD-ROM Dictionnaire généalogique du Québec ancien des origines à 1765.