However , others viewed this interpretation as the impetus for a new wave in the history of United States imperialism .
Many believed that the end of the frontier represented the beginning of a new stage in American life and that the United States must expand overseas .
Others viewed this interpretation as the impetus for a new wave in the history of United States   imperialism .
Many believed that the end of the frontier represented the beginning of a new stage in American life and that the United States must expand overseas .