Who created the frontier thesis, claiming that the frontier experience promoted independence and equality?

The frontier thesis was developed by Frederick Jackson Turner in his influential 1893 essay, "The Significance of the Frontier in American History." Turner posited that the American frontier experience played a crucial role in shaping the national character, particularly by fostering qualities such as individualism, democracy, and equality. He argued that the challenges of the frontier led to the development of a unique American identity, distinct from European influences.

Turner's thesis highlighted the idea that as settlers moved westward, they were able to create new opportunities, escape restrictive social structures, and cultivate a sense of independence that was integral to the American spirit. This notion has significantly impacted how historians interpret the role of westward expansion in American history.

The other figures mentioned did not formulate this thesis; their contributions were in different realms—Rockefeller in industry and oil, Carnegie in steel production and philanthropy, and Twain in literature and social commentary. Thus, Turner's articulation of the frontier as a pivotal aspect of American life remains foundational in understanding the dynamics of U.S. history during this period.