Final answer:
Turner felt the frontier significantly shaped American character and institutions, fostering individualism, innovation, and democracy due to the challenges present there. His Frontier Thesis suggested evolving social and political organizations distinct from European norms, strongly influencing views on American development.
Step-by-step explanation:
Historian Frederick Jackson Turner thought the frontier was significant because he believed it shaped the American character and the institutions of the United States. In his seminal work, "The Significance of the Frontier in American History," presented in 1893, Turner articulated the Frontier Thesis, positing that the existence of a frontier and its settlement had a profound and formative effect on American democracy, culture, and society. He argued that the challenges and opportunities of the frontier made Americans more individualistic, innovative, and democratic.
Turner's thesis emphasized that the moving western frontier line fostered a spirit of self-reliance and that the interactions between settlers and the untamed nature of the frontier necessitated new forms of social and political organization, distinct from those of European societies. This hypothesis significantly influenced historical interpretations of American development and westward expansion for much of the 20th century.