Fort Frontenac occupies a site of national
historic significance. Not only is the Fort central to the military history
of Canada, it is also the earliest site of permanent European habitation in
Ontario. Located at a strategic crossroads of major water routes, the Fort
and the ships based in its harbour, were intended to control all east/west
and north/south traffic in eastern North America. 
Louis de Baude, Conte de Frontenac and Governor of New France, established the first fort in 1673 in an attempt to control the Iroquois. It consisted of palisades, earthworks and log buildings. The first Commandant, Robert Cavalier, Sieur de LaSalle, was to become one of Canada's great explorers and he used the fort as a base for his explorations into the interior of the continent. It was LaSalle who, in 1675, replaced the wood and earth structure with stone walls and bastions and it was during his command that the first ships on Lake Ontario were launched in Cataraqui Harbour.
A few years after the fort
was constructed, open warfare resumed with the Iroquois and the advanced
French posts at Niagara and Cataraqui came under close siege. 
By the spring of 1688, most of the French garrison had died of scurvy and within a year this post was abandoned.
Reoccupied in 1695, the fort played an important part in the subsequent French push into the interior and in their strategic efforts to encircle the English colonies.
In 1758, Lieutenant-Colonel John Bradstreet of the 60th Royal Americans with 3,000 men landed near what is now Queen's University, and moved quickly to set up siege lines around the fort. The small garrison was caught by surprise and after some light resistance, the Commandant, Captaine Pierre-Jacques Payen, Sieur de Noyan, surrendered. Bradstreet proceeded to destroy the French ships captured in the harbour and after patrolling the garrison, he made some ineffective efforts at demolishing the fort's stonework.
Fort Frontenac lay
abandoned until July 1783, when Major John Ross of the British Army arrived
with a small detachment and built barracks on the site of the fort's ruins.
Major Ross' barracks covered the crossing site over the river to the
dockyard and about 1789, were named the Tête-de-Pont (bridgehead) Barracks. 
This temporary post attracted merchants from Carleton Island anxious to ensure continued enterprise on secure ground. These merchants clustered on the grounds adjacent to the garrison and began the civilian occupation of the townsite. Kingston, as the new town was named, became a designated Loyalist re-settlement area, and beginning in 1784 the Loyalists took up their land grants in the town and in the townships to the west.
In the years prior to the War of 1812, the Kingston garrison was normally one or two companies in size at best. Although regular regiments were always stationed in Canada and often occupied the Barracks, the need for troops in the European War encouraged the formation of provincial units and Tête-de-Pont Barracks were occupied at times by some of the earlier Canadian regulars such as the Queen's Rangers, and the Royal Canadian Volunteers.
During the War of 1812, Kingston became the army and navy headquarters for Upper Canada. Men and money flowed into the town and the impetus given by these infusions would see Kingston boom for the next thirty years. Hasty defense works and batteries were thrown up about the town and the first fort was built on Point Henry.
Tête-de-Pont Barracks
became part of an extended military complex in the area. Troops moving to
and from the western battlefields passed through the barracks and here too,
troops were assembled for amphibious attacks on Sackett's harbour and Oswego
.
During the period 1821-1824, the Fort portion of the Barracks was improved by the construction of stone buildings. The outer wall, the officers' mess, the two barrack blocks, and what is now the central heating plant all date from this period. This new construction saw the razing of most of the remaining French fortress. A tower, which stood in the south-east bastion of the old fort, and which appears in several old drawings of the fort, was removed in 1832. Part of the tower's foundation tower and bastion are now exposed in the sunken garden inside the Fort.
Throughout the first half of the 19th Century, Kingston was the key to all defence planning for Upper Canada. Supremacy on the lake was essential to any defence and thus a secure naval station was required. The Rideau Canal and Fort Henry were built to supply and defend the dockyard, and troops in garrison at Fort Frontenac were a key element in the defence plan.
After confederation, relations improved somewhat with the United States, and this allowed the British government to withdraw its garrison from Canada.
To maintain the forts and
armaments transferred to the Dominion government, two batteries of milita
artillery were activated; one in Kingston, one in Quebec city. The
Kingston battery was stationed at Fort Frontenac and was given an increased
establishment of horses to allow riding to be taught to RMC cadets. This set
the tone for the Kingston battery, and in 1905, it was designated as the
Royal Canadian Horse Artillery. Fort Frontenac would remain the home
of the RCHA until December 1939 when they marched out to the gate, onto a
waiting troop train and went to war.

With the departure of 1 RCHA on active service in 1939, the fort became a personnel depot, and after the war in 1947, it became the home for the Canadian Army Staff College and the newly created National Defence College.
In
conclusion, Fort Frontenac, in its different configurations, has witnessed
over three hundred years of Canadian military history. Troops have
mustered within its walls for service in every Canadian campaign from the
Iroquois Wars to World War II, and since 1947, the Fort has been the centre
of professional education for army officers.