What was the passing of the frontier of 1890?

The passing of the frontier in 1890 refers to the U.S. Census Bureau's declaration that the American frontier, defined as a region of unsettled land, had been effectively closed as of that year. This marked a significant shift in American identity and expansion, symbolizing the end of an era of westward expansion and the belief in limitless opportunities. The concept influenced various aspects of American culture, including literature and politics, as it raised questions about the nation's future and the challenges of urbanization and industrialization.