Semisopochnoi Island

Semisopochnoi Island is an uninhabited volcanic island far out in the Aleutian chain, and the source of one of the great geographic riddles of the United States. Because the Aleutians reach so far west that they cross the 180th meridian into the Eastern Hemisphere, Semisopochnoi - sitting at about 179.6 degrees east - is by longitude the easternmost point of the entire country, even though it lies near its far western end.

The same quirk means the U.S. holds both the westernmost and easternmost longitudes on Earth, on islands only a short distance apart. Wreathed in fog and crowned by the active Mount Cerberus volcano, Semisopochnoi is home only to seabirds and sea lions, part of the Alaska Maritime National Wildlife Refuge. It is a place almost no one visits, yet it quietly anchors the outermost edge of American geography.

• Alaska
  The largest U.S. state, a sub-Arctic giant related
• The Aleutian Islands
  A volcanic arc reaching from Alaska toward Asia related