How did frederick turner's frontier thesis affect american imperialism

Historian Frederick Jackson Turner presented his “frontier thesis” in an address in Chicago, the site of the 1893 World’s Columbian Exposition. Turner pointed to expansion as the most important factor in American history. He claimed that “the existence of an area of free land, its continuous recession, and the advance of American settlement westward explain American development.” In 1890, however, the Census Bureau stated that all the land within the United States was claimed, and there was no longer a frontier. “Now, four centuries from the discovery of America, at the end of a hundred years of life under the Constitution, the frontier has gone, and with its going has closed the first period of American history,” Turner asserted, questioning how American culture and history would develop and whether Americans would retain “that coarseness and strength combined with acuteness and acquisitiveness . . . that dominant individualism” bred by expansion now that the frontier was closed.