Royal Flying Corps Hangars
The Royal Flying Corps hangars at Camp Borden are the oldest examples of this type of construction in existence in Canada. These hangars, which are an essential element of the first Canadian military aerodrome, were erected as temporary facilities in 1917, and housed various air training schools. They witnessed the birth of Canada's national air force, the Canadian Air Force in 1920, which became the Royal Canadian Air Force in 1924.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.