What did the last Native American battle signify about the frontier?

The correct answer signifies that the last Native American battle represented a turning point in the American frontier experience. This outcome suggests that the era of expansion and conflict over land was effectively coming to a close. By the time the last major resistance had ended, the United States had largely settled and established control over the continent, leaving little unclaimed land for expansion. This marked the transition of the frontier from a space of conflict and conquest to one of settled governance and societal development.

The significance of this moment also reflects on the diminishing role of Native American resistance and the drastic changes their communities faced due to U.S. policies, settlement, and military actions. With significant resistance effectively quelled, it became evident that the era of westward expansion was concluding, symbolizing the shift in American society's focus from exploration and conquest to consolidation and integration of the territory.