Columbia subject headings:
United States--Economic conditions.
United States--Foreign economic relations.
United States--Foreign relations.
United States--Territorial expansion.
Harvard subject headings:
United States--Economic conditions.
United States--Foreign economic relations.
United States--Foreign relations.
United States--Territorial expansion.
Princeton subject headings:
United States--Economic conditions.
United States--Foreign economic relations.
United States--Foreign relations.
United States--Territorial expansion.