As used in this chapter the term “rural area”, except as provided in section 924 (b) of this title, shall be deemed to mean any area of the United States not included within the boundaries of any urban area, as defined by the Bureau of the Census, and such term shall be deemed to include both the farm and nonfarm population thereof; the term “farm” shall be deemed to mean a farm as defined in the publications of the Bureau of the Census; the term “person” shall be deemed to mean any natural person, firm, corporation, or association; the term “Territory” shall be deemed to include any insular possession of the United States; and the term “Secretary” shall be deemed to mean the Secretary of Agriculture.