Question

How did advocates of expansionism react to Turner's frontier thesis?

Answer 1

The promoters of expansionism respond to Turner's wilderness theory is the point at which they contended Americans should move in the opposite direction of the way of life of the American West and grasp European culture. 
Antiquarian Frederick Jackson Turner displayed his "boondocks proposal" in an address in Chicago, the site of the 1893 World's Columbian Exposition. Turner indicated development as an essential factor in American history. He asserted that "the presence of a territory of free land, its nonstop retreat, and the progress of American settlement westbound clarify American improvement." In 1890, in any case, the Census Bureau expressed that all the land inside the United States was guaranteed, and there was never again an outskirt.