Fort Henry at Kingston, today a National Historic Site, rests on the point that was first fortified in late 1812 to provide protection to the dockyard on Point Frederick (current site of the Royal Military College of Canada). Kingston was home to the Provincial Marine, 1784 to 1813, and to the Royal Navy, 1813 to 1830s. In the spring of 1814, the dockyard was transferred from the Quartermaster General’s Department to the Royal Navy and became an official Royal Navy station. Several warships were constructed there, including the largest warship to serve on the lakes, HMS St Lawrence.

As the naval base, Kingston, at the head of Lake Ontario and at the western end of the River, was involved in countering actions from the American naval centre at Sackets Harbor. After the war, Fort Henry was built (completed 1832) as a military linchpin at the intersection of the three strategic waterways which meet here: the Rideau Canal, the St Lawrence River, and Lake Ontario. Fort Henry is the largest fortification west of Quebec City.

The incident at Bath is a colourful illustration of naval action occurring here during the War of 1812. In November 1812, the British corvette Royal George (22 guns), commanded by Commodore Earle, was intercepted off False Duck Islands by a seven-ship fleet under Commodore Chauncey. While pursued, the Royal George escaped through a gap between Amherst Island and the eastern tip of Prince Edward County into the Bay of Quinte's north channel. The chase resumed in light winds the following day when the Royal George arrived safely in Kingston harbour. Chauncey, intent on capturing the largest British warship then on Lake Ontario, attacked her in the harbour, but withdrew after exchanging fire with the Royal George and with shore batteries.

In the aftermath of the War of 1812, the Rideau Canal was built for strategic military purposes as a supply line to defend Canada (completed 1832). It is now a UNESCO World Heritage Site (along with Fort Henry and the Kingston fortifications) and is recognized as the best-preserved example of a slackwater canal in North America. The canal runs from Kingston Harbour and follows the Rideau River Valley to Ottawa.

The Rideau Military Settlements were established (1816-1822) for demobilized soldiers and British emigrants in the townships adjacent to Perth, Lanark and Richmond. The first military depot was based in Perth. This loyal population received free land grants in return for future defence and protection of Upper Canada. Scottish emigrants were quartered in the barracks at Brockville during the winter of 1815-16 until the survey of the settlement was completed. The soldiers discharged from units, such as the Glengarry Light Infantry and the Swiss regiments of De Meuron and De Watteville, formed a majority of the original settlers. However, the soldiers and family members also came from many diverse demobilized units and from many countries in continental Europe. In large part, the demobilized officers of the units were settled in Perth.

HMS Radcliff, built in 1817, was the last ship of war built on the Great Lakes at Kingston’s dockyards.