The Frontier thesis was formulated 1893, when American historian Frederick Jackson Turner theorized that the availability of unsettled land throughout much of American history was the most important factor determining national development. Frontier experiences and new opportunities forced old traditions to change, institutions to adapt and society to become more democratic as class distinctions collapsed. The result was a unique American society, distinct from the European societies from which it originated. In Canada the frontier thesis was popular between the world wars with historians such as A.R.M. LOWER and Frank UNDERHILL and sociologist S.D. CLARK, partly because of a new sense of Canada's North American character.
Since WWII the frontier thesis has declined in popularity because of recognition of important social and cultural distinctions between Canada and the US. In its place a "metropolitan school" has developed, emphasizing Canada's much closer historical ties with Europe. Moreover, centres such as Montréal, Toronto and Ottawa had a profound influence on the settlement of the Canadian frontier. Whichever argument is emphasized, however, any realistic conclusion cannot deny that both the frontier and the ties to established centres were formative in Canada's development.
See also METROPOLITAN-HINTERLAND THESIS.