The Great Frontier represents a daring attempt to interpret the settlement of the American West in the global context of the expansion of European civilization between the fifteenth and twentieth centuries. According to Webb's boom hypothesis, the expansion of Europe's Great Frontier into the Western Hemisphere energized a static society and made possible the development of such fundamental institutions of the modern era as individualism, capitalism, and political democracy. Webb contends that the closing of the global frontier at the end of the nineteenth century, with the end of easily available empty land and readily exploited natural resources, was responsible for the crises and violence of the twentieth century and boded ill for the future of the United States's treasured democracy.