The Americas, or America, are lands in the Western Hemisphere
that are also known as the New World. Comprising the continents of North
America and South America, along with their associated islands, they cover 8.3%
of the Earth's total surface area (28.4% of its land area). The topography is
dominated by the American Cordillera, a long chain of mountains that run the
length of the west coast.
The flatter eastern side of the Americas is dominated
by large river basins, such as the Amazon, Mississippi, and La Plata. Extending
14,000 km (8,699 mi) in a north-south orientation, the climate and ecology
varies strongly across the Americas, from arctic tundra of Northern Canada,
Greenland, and Alaska, to the tropical rain forests in Central America and
South America. When the continents joined 3 million years ago, the Great
American Interchange resulted in many species being spread across the Americas,
such as the cougar, porcupine, and hummingbirds.
Humans first settled the Americas from Asia between 40,000
BCE and 15,000 BCE. A second migration of Na-Dene speakers followed later from
Asia. The subsequent migration of the Inuit into the neoarctic around 3500 BCE
completed what is generally regarded as the settlement by the Indigenous
peoples of the Americas. The first European discovery of and settlement in the
Americas was by the Norse explorer Leif Ericson. However the colonization never
became permanent and was later abandoned. The voyages of Christopher Columbus
from 1492 to 1502 resulted in permanent contact with European (and subsequently,
other Old World) powers, which led to the Columbian exchange.
Diseases
introduced from Europe and Africa devastated the Indigenous peoples, and the
European powers colonised the Americas. Mass emigration from Europe, including
large numbers of indentured servants, and forced immigration of African slaves
largely replaced the Indigenous Peoples. Beginning with the American Revolution
in 1776 and Haitian Revolution in 1791, the European powers began to decolonise
the Americas. Currently, almost all of the population of the Americas resides
in independent countries; however, the legacy of the colonisation and
settlement by Europeans is that the Americas share many common cultural traits,
most notably the predominant adherence to Christianity and use of Indo-European
languages; primarily Spanish, English, and Portuguese. More than 900 million
people live in the Americas (about 13.5% of the human population), the most
populous countries being the United States, Brazil, and Mexico, the most
populous cities being Mexico City, São Paulo, and New York City.