After the war in 1812, the possibility that the Americans might reactivate their wish to conquer Canada remained a serious concern for at least the next half century, and was the chief reason for the British maintaining a large garrison at the Halifax Citadel (above). The years of the 1820s-40s witnessed fairly extensive fortifications building in the colonies, as the British created strong points (such as the Citadels at Quebec, Halifax, and Fort Henry) around which defending forces might centre in the event of an American invasion. The Rideau Canal was also built during these years to allow ships in wartime to travel a more northerly route from Montreal to Kingston. The customary peacetime route was the St. Lawrence River, which, of course, constituted the northern edge of the American border, and hence was vulnerable to enemy attack and interference.

The present Halifax Citadel (above) was built starting in 1828. It was completed in 1856 after numerous delays due to design and structural problems. Shortly afterward, the introduction of rifled artillery rendered the fort obsolete. It continued to be used as a barracks into the 20th century and was handed over to the Canadian militia when the British pulled out in 1906

Sources

Various web sites