Alaska in the context of Western North America

The Americas, sometimes collectively called America, are a landmass comprising the totality of North America and South America. When viewed as a single continent, the Americas are the 2nd largest continent by area after Asia and the 3rd largest continent by population. The Americas make up most of the land in Earth's Western Hemisphere and constitute the New World.

Along with their associated islands, the Americas cover 8% of 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 runs the length of the west coast. The flatter eastern side of the Americas is dominated by large river basins, such as the Amazon, St. Lawrence River–Great Lakes, Mississippi, and La Plata basins. 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 rainforests in Central America and South America.

A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high discharge. The soils usually consist of clays, silts, sands, and gravels deposited during floods.

Because of regular flooding, floodplains frequently have high soil fertility since nutrients are deposited with the flood waters. This can encourage farming; some important agricultural regions, such as the Nile and Mississippi river basins, heavily exploit floodplains. Agricultural and urban regions have developed near or on floodplains to take advantage of the rich soil and freshwater. However, the risk of inundation has led to increasing efforts to control flooding.

The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 states and a federal capital district, Washington, D.C. The 48 contiguous states border Canada to the north and Mexico to the south, with the semi-exclave of Alaska in the northwest and the archipelago of Hawaii in the Pacific Ocean. The United States also asserts sovereignty over five major island territories and various uninhabited islands in Oceania and the Caribbean. It is a megadiverse country, with the world's third-largest land area and third-largest population, exceeding 340 million.

Paleo-Indians first migrated from North Asia to North America over 12,000 years ago, and formed various civilizations. Spanish colonization established Spanish Florida in 1513, the first European colony in what is now the continental United States. British colonization followed with the 1607 settlement of Virginia, the first of the Thirteen Colonies. Enslavement of Africans was practiced in all colonies by 1770 and supplied most of the labor for the Southern Colonies' plantation economy. Clashes with the British Crown over taxation and lack of parliamentary representation sparked the American Revolution, leading to the Declaration of Independence on July 4, 1776. Victory in the 1775–1783 Revolutionary War brought international recognition of U.S. sovereignty and fueled westward expansion, dispossessing native inhabitants. As more states were admitted, a North–South division over slavery led the Confederate States of America to attempt secession and fight the Union in the 1861–1865 American Civil War. With the United States' victory and reunification, slavery was abolished nationally. By 1900, the country had established itself as a great power, a status solidified after its involvement in World War I. Following Japan's attack on Pearl Harbor in 1941, the U.S. entered World War II. Its aftermath left the U.S. and the Soviet Union as rival superpowers, competing for ideological dominance and international influence during the Cold War. The Soviet Union's collapse in 1991 ended the Cold War, leaving the U.S. as the world's sole superpower.

Northern America is the northernmost subregion of North America, as well as the northernmost region in the Americas. The boundaries may be drawn significantly differently depending on the source of the definition. In one definition, it lies directly north of Middle America. Northern America's land frontier with the rest of North America then coincides with the Mexico–United States border. Geopolitically, according to the United Nations' scheme of geographical regions and subregions, Northern America consists of Bermuda, Canada, Greenland, Saint Pierre and Miquelon and the United States (the contiguous United States and Alaska only, excluding Hawaii, Navassa Island, Puerto Rico, the United States Virgin Islands, and other minor U.S. Pacific territories).

Northern Canada (French: le Nord du Canada), colloquially the North or the Territories, is the vast northernmost region of Canada, variously defined by geography and politics. Politically, the term refers to the three territories of Canada: Yukon, Northwest Territories and Nunavut. This area covers about 48 per cent of Canada's total land area, but has less than 0.5 per cent of Canada's population.

The terms "northern Canada" or "the North" may be used in contrast with the far north, which may refer to the Canadian Arctic, the portion of Canada that lies north of the Arctic Circle, east of Alaska and west of Greenland. That said, in many other uses the two areas are treated as a single unit.

In the United States, a county or county equivalent is an administrative subdivision of a state or territory, typically with defined geographic boundaries and some level of governmental authority. The term "county" is used in 48 states, while Louisiana and Alaska have functionally equivalent subdivisions called parishes and boroughs, respectively. Counties and other local governments exist as a matter of U.S. state law, so the specific governmental powers of counties may vary widely between the states, with many providing some level of services to civil townships, municipalities, and unincorporated areas. Certain municipalities are in multiple counties. Some municipalities have been consolidated with their county government to form consolidated city-counties or have been legally separated from counties altogether to form independent cities. Conversely, counties in Connecticut and Rhode Island, eight of Massachusetts's 14 counties, and Alaska's Unorganized Borough have no government power, existing only as geographic distinctions.

The United States Census Bureau uses the term "county equivalent" to describe places that are comparable to counties, but called by different names. Louisiana parishes, the organized boroughs of Alaska, independent cities, and the District of Columbia are equivalent to counties for administrative purposes. Alaska's Unorganized Borough is further divided into 11 census areas that are statistically equivalent to counties. In 2024, the U.S. Census Bureau began to also recognize Connecticut's councils of governments, which took over some of the regional powers from the state's former county governments, as county equivalents.

A borough in some U.S. states is a unit of local government or other administrative division below the level of the state. The term is currently used in six states:

• A type of municipality: Connecticut, New Jersey and Pennsylvania (also formerly Michigan and Minnesota)
• A subdivision of a consolidated city, corresponding to another present or previous political subdivision: New York and Virginia
• In Alaska only, a borough is a county-equivalent.

Rail transport (also known as train transport) is a means of transport using wheeled vehicles running on tracks, which usually consist of two parallel steel rails. Rail transport is one of the two primary means of land transport, next to road transport. It is used for about 8% of passenger and freight transport globally, thanks to its energy efficiency and potentially high speed. Also, the track spreads the weight of the train which means larger amounts can be carried than with trucks on roads.

Rolling stock on rails generally encounters lower frictional resistance than rubber-tyred road vehicles, allowing rail cars to be coupled into longer trains. Power is usually provided by diesel or electric locomotives. While railway transport is capital-intensive and less flexible than road transport, it can carry heavy loads of passengers and cargo with greater energy efficiency and safety.

It is believed that the peopling of the Americas began when Paleolithic hunter-gatherers (Paleo-Indians) entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the Last Glacial Maximum (26,000 to 19,000 years ago). These populations expanded south of the Laurentide Ice Sheet, either by sea or land, and spread rapidly southward, occupying both North and South America no later than 14,000 years ago, and possibly before 20,000 years ago. The earliest populations in the Americas, before roughly 10,000 years ago, are known as Paleo-Indians. Indigenous peoples of the Americas have been linked to Siberian populations by proposed linguistic factors, the distribution of blood types, and in genetic composition as reflected by molecular data, such as DNA.

While there is general agreement that the Americas were first settled from Asia, the pattern of migration and the place(s) of origin in Eurasia of the peoples who migrated to the Americas remain unclear. The most generally accepted theory is that Ancient Beringians moved when sea levels were significantly lowered due to the Quaternary glaciation, following herds of now-extinct Pleistocene megafauna along ice-free corridors that stretched between the Laurentide and Cordilleran ice sheets. Another proposed route has them migrating down the Pacific coast to South America as far as Chile, either on foot or using boats. Any archaeological evidence of coastal occupation during the last Ice Age would now have been covered by the sea level rise, up to a hundred metres since then.

In geography and geology, fluvial sediment processes or fluvial sediment transport are associated with rivers and streams and the deposits and landforms created by sediments. It can result in the formation of ripples and dunes, in fractal-shaped patterns of erosion, in complex patterns of natural river systems, and in the development of floodplains and the occurrence of flash floods. Sediment moved by water can be larger than sediment moved by air because water has both a higher density and viscosity. In typical rivers the largest carried sediment is of sand and gravel size, but larger floods can carry cobbles and even boulders.When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvioglacial is used, as in periglacial flows and glacial lake outburst floods. Fluvial sediment processes include the motion of sediment and erosion or deposition on the river bed.

The history of exploration by citizens or subjects of the Russian Federation, the Soviet Union, the Russian Empire, the Tsardom of Russia and other Russian predecessor states forms a significant part of the history of Russia as well as the history of the world. At 17,075,400 square kilometres (6,592,850 sq mi), Russia is the largest country in the world, covering more than a ninth of Earth's landmass. In the times of the Soviet Union and the Russian Empire, the country's share in the world's landmass reached 1/6. Most of these territories were first discovered by Russian explorers (if indigenous peoples of inhabited territories are not counted). Contiguous exploration in Eurasia and the building of overseas colonies in Russian America were some of the primary factors in Russian territorial expansion.

Apart from their discoveries in Alaska, Central Asia, Siberia, and the northern areas surrounding the North Pole, Russian explorers have made significant contributions to the exploration of the Antarctic, Arctic, and the Pacific islands, as well as deep-sea and space explorations.

Geographic contiguity is the characteristic in geography of political or geographical land divisions, as a group, not being interrupted by other land or water. Such divisions are referred to as being contiguous. In the United States, for example, the "48 contiguous states" excludes Hawaii and Alaska, which do not share borders with other U.S. states.

Other examples of geographical contiguity might include the "contiguous European Union" excluding member states such as Ireland, Sweden, Finland (between Åland and Turku Archipelago), Malta and Cyprus (these being non-contiguous), or the "contiguous United Kingdom" referring to all parts of the country excepting Northern Ireland (it being geographically non-contiguous).

The Bering Strait (/ˈbɛərɪŋ, ˈbɛrɪŋ/ BAIR-ing, BERR-ing, US also /ˈbɪərɪŋ/ BEER-ing; Russian: Берингов пролив, romanized: Beringov proliv) is a strait between the Pacific and Arctic oceans, separating the Chukchi Peninsula of the Russian Far East from the Seward Peninsula of Alaska. The present Russia–United States maritime boundary is at 168° 58' 37" W longitude, slightly south of the Arctic Circle at about 65° 40' N latitude. The Strait is named after Vitus Bering, a Danish-born Russian explorer.

The Bering Strait has been the subject of the scientific theory that humans migrated from Asia to North America across a land bridge known as Beringia when lower ocean levels – a result of glaciers locking up vast amounts of water – exposed a wide stretch of the sea floor, both at the present strait and in the shallow sea north and south of it. This view of how Paleo-Indians entered America has been the dominant one for several decades and continues to be the most accepted one. Numerous successful crossings without the use of a boat have also been recorded since at least the early 20th century.

Hawaii (/hə.ˈwaɪ.i/ hə-WY-ee; Hawaiian: Hawaiʻi [hə.ˈvɐj.ʔi, hə.ˈwɐj.ʔi]) is an island state of the United States, in the Pacific Ocean about 2,000 miles (3,200 km) southwest of the U.S. mainland. One of the two non-contiguous U.S. states (along with Alaska), it is the only state not on the North American mainland, the only state that is an archipelago, the only state in the tropics, and one of the two U.S. states, along with Texas, that were internationally recognized sovereign countries before becoming U.S. states.

Hawaii consists of 137 volcanic islands that make up almost the entire Hawaiian archipelago (the exception is Midway Atoll). Spanning 1,500 miles (2,400 km), the state is physiographically and ethnologically part of the Polynesian subregion of Oceania. Hawaii's ocean coastline is consequently the fourth-longest in the U.S., at about 750 miles (1,210 km). The eight main islands, from northwest to southeast, are Niʻihau, Kauaʻi, Oʻahu, Molokaʻi, Lānaʻi, Kahoʻolawe, Maui, and Hawaiʻi, after which the state is named; the last is often called the "Big Island" or "Hawaiʻi Island" to avoid confusion with the state or archipelago. The uninhabited Northwestern Hawaiian Islands make up most of the Papahānaumokuākea Marine National Monument, the largest protected area in the U.S. and the fourth-largest in the world.