In 1893, the American Historical Association met during that year’s World’s Columbian Exposition in Chicago. The young Wisconsin historian Frederick Jackson Turner presented his “frontier thesis,” one of the most influential theories of American history, in his essay, “The Significance of the Frontier in American History.”

Turner looked back at the historical changes in the West and saw, instead of a tsunami of war and plunder and industry, waves of “civilization” that washed across the continent. A frontier line “between savagery and civilization” had moved west from the earliest English settlements in Massachusetts and Virginia across the Appalachians to the Mississippi and finally across the Plains to California and Oregon. Turner invited his audience to “stand at Cumberland Gap [the famous pass through the Appalachian Mountains], and watch the procession of civilization, marching single file—the buffalo following the trail to the salt springs, the Indian, the fur trader and hunter, the cattle-raiser, the pioneer farmer—and the frontier has passed by.”

Americans, Turner said, had been forced by necessity to build a rough-hewn civilization out of the frontier, giving the nation its exceptional hustle and its democratic spirit and distinguishing North America from the stale monarchies of Europe. Moreover, the style of history Turner called for was democratic as well, arguing that the work of ordinary people (in this case, pioneers) deserved the same study as that of great statesmen. Such was a novel approach in 1893.

But Turner looked ominously to the future. The Census Bureau in 1890 had declared the frontier closed. There was no longer a discernible line running north to south that, Turner said, any longer divided civilization from savagery. Turner worried for the United States’ future: what would become of the nation without the safety valve of the frontier? It was a common sentiment. Theodore Roosevelt wrote to Turner that his essay “put into shape a good deal of thought that has been floating around rather loosely.”

The history of the West was many-sided and it was made by many persons and peoples. Turner’s thesis was rife with faults, not only its bald Anglo Saxon chauvinism—in which non-whites fell before the march of “civilization” and Chinese and Mexican immigrants were invisible—but in its utter inability to appreciate the impact of technology and government subsidies and large-scale economic enterprises alongside the work of hardy pioneers. Still, Turner’s thesis held an almost canonical position among historians for much of the twentieth century and, more importantly, captured Americans’ enduring romanticization of the West and the simplification of a long and complicated story into a march of progress.

This chapter was edited by Lauren Brand, with content contributions by Lauren Brand, Carole Butcher, Josh Garrett-Davis, Tracey Hanshew, Nick Roland, David Schley, Emma Teitelman, and Alyce Vigil.