He was elected to the Legislative Assembly of the Province of Canada for Vaudreuil in 1844.
In 1865, Lantier married Julienne Bonneville, the widow of his brother Olivier, who had been a merchant at Montreal.
He was elected to the House of Commons in 1872 and represented Soulanges until his death at Saint-Polycarpe in 1882.
Lantier published the pamphlets Canal des Cèdres (1873), The harbours of Coteau Landing and Cascades Bay (1874), and The question of the Cascades and Coteau Landing canal (1874).
In 1873, Lantier introduced a motion in the House of Commons asking for a pardon for all crimes committed in Manitoba before its entry into the Canadian union.
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