Étienne Verrier was born not far from Marseille, a French port on the Mediterranean. He learned to work in stone early in his life as his father was a "master-sculptor." In 1707, Verrier moved to La Rochelle, a French port on the Atlantic; there he took up a position with the French military corps. In 1720, at age 37, he was sent on a military cruise to the east (present day Vietnam). Having arrived back at La Rochelle, in 1724, Verrier was ordered to go to New France and there to take up his duties as Resident Chief Engineer at Louisbourg. For the first year Verrier worked under the director of fortifications, Jean-François de Verville. But the with transfer of Verville and the elimination of the position of director, Verrier had a relatively free hand in the development of the fortifications at Louisbourg.
Verrier carried out his duties at Louisbourg between the occasional visits to his family1 back in France and left much of the detail of the work to his two assistants, Couagne and Boucher.
History recognizes Verville as the builder of Louisbourg; not only the fortifications, but also the chief public buildings, the lighthouse, the whole harbour front; and his talents were not restricted in their exercise just to Louisbourg, the fortifications at Port-Dauphin (Englishtown), Port-Toulouse (St Peters) and Port-La-Joie (P.E.I.) came into existence under his direction.
As might be imagined, Verrier held a powerful position at Louisbourg. He, however, like all of the French leaders behind the walls during the first siege was lacking in "siegecraft."2 He was instrumental in the decision to surrender the fort to the New Englanders.
Verrier left Louisbourg for France along with the other defeated French officers in 1745.3 On returning to France Verrier did get another military appointment which allowed him to spend his last years at La Rochelle. Verrier died two years later in 1747.
 DCB, vol. III, p. 645.
 An interesting foot note is that Verrier took all of the fortification plans with him when he sailed away from Louisbourg which didn't seem to bother the conquering New Englanders at the time, but which bothered the French, when, in 1749, the fort was returned back to the French. By 1749, Verrier was dead and his wife held the plans and refused to give them up until the government settled the accounts which figured it had with the estate. I do not know how all of that turned out, but, to-day, Verrier's original plans, over a hundred of them, are preserved at Parisian depositories such as the Archives Nationales.