According to Frederick Jackson Turner, what did the 1890 Census signify for the American frontier?

Frederick Jackson Turner argued that the 1890 Census signified the closure of the American frontier, marking a pivotal transformation in American identity and society. Turner's "Frontier Thesis" posited that the frontier had been crucial in shaping American democracy, individualism, and national character. He believed that with the announcement of the Census showing no discernible frontier line, the era of westward expansion had effectively come to an end.

This conclusion led to significant discussions regarding what would come next for the United States and how the country's identity would evolve now that the frontier was no longer an active space for settlement and opportunity. The implications of this were vast, suggesting shifts towards urbanization, industrialization, and dealing with social issues born out of a more crowded, industrial society, but Turner specifically focused on this notion of frontier closure as a critical juncture in American history.