Grandmaison, a carpenter from Quebec City, moved to Beaubassin after the death of his first wife in 1749. In 1752.

He married Marguerite Thibodeau, daughter of Jean-Baptiste and Marguerite Leblanc, and granddaughter of the founder of Shepody.

In 1754, he sold his property for a large profit to the commander of Fort Beausejour, who paid him (illegally) with goods from the military store.

He then moved to Kamouraska, where in 1757 he was buying property and being referred to as a "merchant trader;

He was also the administrator of the Kamouraska seigneury owned by Jean' Baptiste d'Amours and commander of the French forces on the St. John River.

Some Acadians refugees joined Jean-Baptiste Grandmaison after 1755---and in 1761 Marguerite Grandmaison-Thibodeau was godmother to her niece Marguerite Cyr, daughter of Joseph and Marguerite Blanche Thibodeau, the future Tante Blanche.

Joining Grandmaison was a wise move, since he had widespread business contacts and could help the refugees.

Some French, Acadians, and Natives kept fighting in northeaster New Brunswick after the fall of Montreal in 1760.

The British destroyed the French vessels in the Battle of Restigouche, and Murray, military governor of Quebec, send(sic) an emisssary to the Restigouche Acadians to convince them to lay down their arms;

he promised them land in what is now eastern Ontario

This emissary was Jean-Baptiste Grandmaison, who was wounded in the process and subsequently received a pension from the government.

After 1768, Grandmaison settled at Cacouna and became a militia captain.

He engaged in a variety of economic activities, operated a mill at Riviere Ouelle, and owned a boat.

His business partners included Malcolm Fraser, by then seigneur of Riviere du Loup.

Unfortunately, Grandmaison went bankrupt, and his creditors even garnished his pension. His daughter, Marguerite, and her second husband Antoine Gagne, were among the first Madawaska settlers.

Source: The Land In Between, The Upper St. John Valley, Prehistory to World War I, Beatrice Craig and Maxime Dagenais, Lisa Ornstein and Guy Dubay, c. 2009, pg. 46