what effect do you think the frontier played in american history? How would the closing of the frontier change this?

How did the american revolutionary war change how some americans viewed the enslavement of african americans?

Why was the u.s. annexation of hawaii delayed until william mckinley became president? a: the rebels who overthrew queen liliuokalani opposed u.s. annexation. b: the senate did not approve the treaty of annexation until mckinley entered the white house. c: supporters of the nationalist cause were in the majority in hawaii until 1898. d: mckinley’s predecessor, grover cleveland, refused to sign the treaty of annexation.

What new weapon made allied leaders worry about the cost of invading the japanese mainland?