Laurentian Thesis, an influential theory of economic and national development set forth by several major English Canadian historians from the 1930s through the 1950s. The theory received its most sustained and sophisticated expression in the writings of Donald CREIGHTON, especially The COMMERCIAL EMPIRE OF THE ST. LAWRENCE (1937). Creighton argued that Canadian economic and national development derived fundamentally from the gradual exploitation of key staple products - fur, timber and wheat - by colonial merchants in the major metropolitan centres of the ST LAWRENCE RIVER system. That system provided the means by which both a transatlantic and a transcontinental market economy could be created. In stressing the connection with the metropolitan capitals of Europe, Creighton undermined the CONTINENTALISM implicit in American historian Frederick Jackson Turner's FRONTIER THESIS while emphasizing environmental factors.
In Creighton's view, the 1885 completion of the CANADIAN PACIFIC RAILWAY marked an extension of the potential for national development inherent in the St Lawrence system. Creighton's theory was derived in part from the STAPLE THEORY advanced by H.A. INNIS, particularly in The Fur Trade in Canada (1930), in which Innis emphasized the importance of European linkages and determining environmental factors.
The Laurentian thesis, given complete expression by Innis and Creighton by 1940, was a major influence on historians writing after WWII. It was not, however, without critics. In a 1946 address called "Clio in Canada: the Interpretation of Canadian History" (published in University of Toronto Quarterly), W.L. MORTON warned of the potential for cultural and regional exploitation inherent in the expansion of central Canadian commerce and institutions, nevertheless accepting as historical fact, here and in The Kingdom of Canada (1963), the development made possible by the Laurentian waterway. J.M.S. CARELESS's publication, Canada: A Story of Challenge (1953), also built upon the theory, although Careless paid closer attention to regional differentiation and metropolitan influence (see METROPOLITAN-HINTERLAND THESIS).
Since 1960 the Laurentian thesis has received much scholarly debate, particularly (as Morton warned) because it rests upon imperial exploitation and control over regional hinterlands. With the regionalization of the historical profession, and with the rise of a SOCIAL HISTORY sensitive to regional and class exploitation, most recent discussion has been critical; nevertheless, even under attack it continues to be the mechanism of historical synthesis against which all others must compete as a means of explaining Canadian history.