PAs Europe exploded everywhere in 1812 with Napoleon invading Russia, Spain descending into chaos, Britain and France in a death grip with each other and Germany awakening to a new nationalism, relations between Britain and the United States also began to fall apart. The War of 1812 opened with several actions along the current Canada US boarder and both sides scrambling to prepare for the fight.
In Upper Canada, the strategic location at the end of the Great Lakes and the beginning of the St Lawrence River became a key point along the front. The British began almost immediately to construct a Fort at Point Henry which was located close to the Royal Navy Dockyard which hosts the Royal Military College today. If the US had captured this area, the British colonies in North American would effectively be cut in half. By 1814 Fort Henry was completed but at wars end it was intact and secure.
As the British colonies continued to grow the Rideau canal was pushed through, 1826 - 32, from Kingston to Bytown (present day Ottawa) and connected the Great Lakes and the St Lawrence with the North. The location of Kingston and Fort Henry had become the strategic focal point of the entire transportation system in British North America.
It was decided that Fort Henry needed to be upgraded and the current Fort Henry was begun in 1832 and finished in 1837. It is the largest fortification west of Quebec city d cost 70,000 pounds to build or about 42,000,000 in today's funds. The British moved out of the Fort in the 1870's and in August of 1938 it was opened as a museum.