Western Hemisphere

The Western Hemisphere is one of the two conventional halves of Earth, defined geographically as all territory lying west of the IERS Reference Meridian through Greenwich, London, and east of the 180th meridian. Although this definition is precise and global, the term is frequently used as a metonym in political and cultural contexts to refer specifically to the Americas or the New World. In strict geographical terms, however, the hemisphere encompasses substantial portions of Europe, Africa, Asia and Oceania, as well as large sectors of Antarctica.

Geographical Extent and Characteristics

Under the prime meridian–180th meridian definition, the Western Hemisphere comprises the entire American landmass with the exception of a few Aleutian Islands extending beyond 180°W. It also includes the westernmost fringes of Europe and Africa, including Portugal, parts of Spain and France, and sections of West Africa. The eastern extremity of Russia’s Chukotka Autonomous Okrug appears in the hemisphere, as do numerous Pacific island groups. Large parts of Antarctica fall within this hemisphere, reflecting the longitudinal breadth of the definition.
The hemispheric centre lies in the Pacific Ocean near the confluence of 90°W and the Equator, positioned among the Galápagos Islands. Genovesa Island lies closest to this theoretical midpoint.
Prominent geographical superlatives within the hemisphere include Aconcagua in Argentina, the tallest mountain in the Western Hemisphere at nearly 7,000 metres. In the built environment, the CN Tower in Toronto and One World Trade Center in New York City represent the tallest freestanding structure and tallest building in the hemisphere, respectively.

Alternative Boundary Definitions

Some scholars and organisations seek to align the Western Hemisphere more closely with the Americas by shifting the delimiting meridians to 20°W and its antipode at 160°E. This narrower definition excludes the European and African mainlands but retains certain Atlantic islands, parts of eastern Russia and portions of Oceania and Antarctica. Under this scheme, all Alaskan islands fall within the hemisphere, while a small segment of northeast Greenland does not. Notably, no longitudinal definition exists that encompasses all of the Americas without simultaneously including some territory from other continents.

States Straddling Both Hemispheres

Certain sovereign states lie in both Western and Eastern hemispheres due to the intersection of their territories with the prime meridian or the 180th meridian.
Along the IERS Reference Meridian (Prime Meridian):

• United Kingdom: The meridian passes through Greenwich; most of the country lies west of it.
• France: Approximately one-eighth of metropolitan France lies west of the meridian, including cities such as Bordeaux and Nantes, alongside western-hemisphere overseas departments.
• Spain: The line passes through Castellón de la Plana; much of Spain and its Canary Islands fall within the Western Hemisphere.
• Algeria: Around 14% of its territory, including Oran, lies to the west.
• Mali, Burkina Faso, Ghana, Togo: These West African countries have large areas situated west of the meridian, including several national capitals.

Other European states such as Denmark and Norway appear on the meridian due to outlying dependencies (Greenland, the Faroe Islands, Jan Mayen), though their metropoles lie entirely in the Eastern Hemisphere. The Netherlands is similarly represented because its Dutch Caribbean territories fall in the Western Hemisphere.
Along the 180th Meridian:

• Russia: The far eastern extremity of Chukotka crosses into the Western Hemisphere.
• United States: Parts of the Aleutian Islands lie west of 180°; other Pacific territories, although near the meridian, sit east of it.
• Kiribati: Uniquely spans all four hemispheres—north, south, east and west—because both the Equator and 180° meridian intersect its islands.
• Tuvalu, Fiji, New Zealand: Several islands or dependencies extend into the Western Hemisphere, including Rotuma, Taveuni, the Chatham Islands and the Kermadec Islands. Associated states such as the Cook Islands and Niue also occupy this region.

Territories in the Western Hemisphere Beyond the Americas

While the hemisphere is often equated with the New World, several non-American lands fall wholly or partly within its bounds:
Africa:

• Portugal (via Atlantic islands)
• Western Sahara (under disputed sovereignty)
• Portions of coastal West Africa including areas of Morocco, Mauritania and neighbouring territories

Antarctica:

• Regions claimed or administered by countries such as Norway, the United Kingdom, Argentina and Chile, including Peter I Island, the South Orkney Islands and the South Shetland Islands.

Asia:

• Easternmost Russia, particularly Chukotka.

Europe:

• Parts of the United Kingdom, France, Spain and Portugal lie within the hemisphere due to their western coastlines and island possessions.

Oceania:

• Numerous island states and territories, including those administered by the United States and New Zealand, fall west of the 180th meridian.

Geopolitical Usage

Government agencies, international organisations and academic literature commonly use Western Hemisphere as shorthand for the Americas in political, economic and cultural contexts. Institutions ranging from the United States Department of State to international trade organisations apply the term in this metonymic sense. Despite its widespread use, this convention masks the more complex geographical reality.
The Western Hemisphere thus functions simultaneously as a precise geographical designation and a broader cultural-political concept. Its physical boundaries encompass a diverse array of territories, climates and populations, while its geopolitical definition reflects the historical and cultural identity associated with the New World.