**UNITED STATES (U.S.A.).** - A confederation of 48 States, one federal District (D.C.) and two territories (Alaska and the Hawaiian Islands), upon which depend, in America, Puerto Rico, the Virgin Islands (Antilles) and the Canal Zone (of Panama), and in Oceania some of the Samoa Islands and Guam (Mariana Islands), as well as the islands of Micronesia formerly under Japanese mandate, which the U.S.A. hold in trusteeship.
**I. GEOGRAPHY.** - Even when considered solely for the extent of their metropolitan territory (7,827,076 sq. km., including 117,207 sq. km. of inland waters, but excluding 156,172 sq. km. pertaining to the federal portion of the Great Lakes, which the U.S.A. share with neighboring Canada), the U.S.A. rank among the largest powers on earth. Including Alaska (destined to become the 49th State of the Union), this area rises to 9.5 million sq. km. (1/16 of the emerged lands). Combining metropolitan territory and dependencies, the U.S.A. exceed 11 million sq. km., yet rank 4th in the world after the British Commonwealth, the U.S.S.R. and the French Union, despite possessing a greater area than all of Europe.
Due to the position of their metropolitan territory, the U.S.A. differ from other major world powers in being in direct contact with only two other States — Canada to the N., Mexico to the S. (whose borders are largely conventional) — even though their international stature engages them in the political issues of every corner of the earth. Such a vast territory, which alone occupies more than 1/3 of the North American continent and far exceeds its ecumenical area, cannot but present notable regional differences. In essence, however, its structure is rather simple: a great central plain stretching from the Great Lakes to the Gulf of Mexico, flanked on the W. (Pacific) and E. (Atlantic) by two mountain ranges that segregate it from the direct influence of the ocean. Of the two ranges, the eastern one, slimmer (Appalachians or Alleghenies), is formed by a bundle of