The Americas, or America, also known as the Western Hemisphere and the New World, comprise the totality of territories in North America and South America.
Along with their associated islands, they cover 8% of the Earth's total surface area and 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. Since the Americas extend 14,000 km (8,700 mi) from north to south, the climate and ecology vary widely, from the arctic tundra of Northern Canada, Greenland, and Alaska, to the tropical rain forests in Central America and South America.
Humans first settled the Americas from Asia between 42,000 and 17,000 years ago. 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.