Why was the Pacific Northwest referred to as the final frontier"?
A. The country that claimed the Pacific Northwest would ultimately claim all remaining uncharted territory across the globe.
B. The exploration and settlement of the Pacific Northwest marked the end of all exploration by the world powers.
C. The Pacific Northwest was the last known uncharted territory that the world powers believed they could claim.
D. The Pacific Northwest was the site of the last battle between the native people and European settlers.