<P> During World War II, Toronto became a major centre for Canada's military . The Exhibition Grounds were taken over for military training and deployment . The Island Airport was taken over for training of the Norwegian Air Force and the Royal Canadian Air Force . Civilian manufacturing companies, such as Inglis, were converted to war - time production of armaments . At Malton Airport and Downsview Airport, new aviation factories built many fighters and bombers to be used in Europe . </P> <P> After World War II, a continuous influx of newcomers from Atlantic Canada and large numbers of immigrants from around the world contributed to the steady growth of Toronto . The large numbers of new Canadians helped Toronto's population swell to over one million by 1951, and double again to over two million, by 1971 . The demographics of Toronto changed as a result also, as many immigrants were from countries other than Great Britain . The ethnic diversity grew and saw the development of enclaves such as Little Italy, Little Portugal and two new Chinatowns . In 1967, the first "Caribana" festival was held celebrating the culture of the West Indies . </P> <P> The provincial government created the Municipality of Metropolitan Toronto, a regional government that incorporated numerous local municipalities in 1954 . The Metro Toronto government took over the construction and maintenance of region - wide infrastructure, building water treatment plants, roads, public transit and expressways, to facilitate the growth of the suburbs . </P> <P> In 1954, Hurricane Hazel swept through Toronto, causing significant flooding; 81 people were killed . As a result, building on floodplains was banned, new flood control works such as dams and flood channels were built, and the lands of floodplains were cleared of buildings, conserved as park lands and conservation areas . </P>

When did toronto become the largest city in canada