After Newfoundland and Acadia were ceded to England by the Treaty of Utrecht (1713), France decided to fortify Cape Breton Island in order to protect Canada, maintain its position on the Atlantic and ensure the exploitation of the abundant fisheries off the coast of Newfoundland. Cape Breton Island became Île Royale. The Secretary of State for the Marine decided to erect a fortress at Louisbourg. The fortified town was designed by military engineers under the direction of Jean-François Verville, according to the fortification theories of the commissary general of fortifications, Sébastien Le Prestre de Vauban. The main defence works were carried out under Étienne Verrier. A large sector was given over to defensive functions. However, since the area's steeply embanked shoreline and the marshes surrounding the fortress were thought sufficient to preclude any attack, the land was not fortified. Beyond its defensive role, Louisbourg soon became an important port, and the hub of exchange for France, the West Indies and Canada. The fortified town included half the population of Île Royale, about 4,000 in 1750, and a large proportion of soldiers were quartered there in barracks. The English took control of Louisbourg in 1745, but Île Royale was given back in 1748. It fell permanently to the English in 1758.

Plan et façades de la porte Dauphine [Plan and façades of Porte Dauphine], 1733
FR CAOM C 11B 39 no 41