Columbia subject headings:
Environmental policy--United States--History.
Nature--Effect of human beings on--United States--History.
United States--Environmental conditions.
United States--Historical geography.
Harvard subject headings:
Environmental geography--United States.
United States--Environmental conditions.
United States--Historical geography.
Princeton subject headings:
Environmental policy--United States--History.
Nature--Effect of human beings on--United States--History.
United States--Environmental conditions.
United States--Historical geography.