 | |
| Continent | North America (except Hawaii and territories) |
|---|---|
| Coordinates | 40°N100°W / 40°N 100°W /40; -100 |
| Area | Ranked 3rd/4th |
| • Total | 9,833,517 km2 (3,796,742 sq mi) |
| • Land | 93.02% |
| • Water | 6.98% |
| Coastline | 151,475 km (94,122 mi) |
| Borders | 12,036 km (7,479 mi) Canada: 8,891 km (5,525 mi) Mexico: 3,145 km (1,954 mi) |
| Highest point | Denali/Mount McKinley 6,190.5 m (20,310 ft) |
| Lowest point | Badwater Basin (Death Valley), −86 m (−282 ft) |
| Longest river | Missouri River, 3,767 km (2,341 mi) |
| Largest lake | (shared)Lake Superior 53,348 km2 (20,598 sq mi) (U.S.) (internal)Lake Michigan 57,757 km2 (22,300 sq mi) |
| Climate | Diverse: Ranges from warm-summer continental in the far north to tropical in the far south. West: mostly semi-arid to desert, Mountains: alpine, Northeast: humid continental, Southeast: humid subtropical, Coast of California: Mediterranean, Pacific Northwest: cool temperate oceanic, Alaska: mostly subarctic, Hawaii, South Florida, and the territories: tropical |
| Terrain | Vast central plain, Interior Highlands and low mountains in Midwest, mountains and valleys in the mid-south, coastal flatland near the Gulf and Atlantic coasts, complete with mangrove forests and temperate, subtropical, and tropical laurel forest and jungle, canyons, basins, plateaus, and mountains in west, hills and low mountains in east; intermittent hilly and mountainous regions in Great Plains, with occasional badland topography; rugged mountains and broad river valleys in Alaska; rugged, volcanic topography in Hawaii and the territories |
| Natural resources | Coal, copper, lead, molybdenum, phosphates, rare earth elements, uranium, bauxite, gold, iron, mercury, nickel, potash, silver, tungsten, zinc, petroleum, natural gas, timber, arable land |
| Natural hazards | Tsunamis; volcanoes; earthquake activity around Pacific Basin; hurricanes along the Atlantic and Gulf of Mexico coasts; severe convective thunderstorms and tornadoes in the Mideast, Great Plains and Southeast; mud slides in California; forest and brush fires in the west and central regions, especially; flooding; dust storms in western and central regions; permafrost in northern Alaska |
| Environmental issues | Environmental issuesDeforestation, energy irresponsibility, pollution, nuclear waste, Severe water shortages, air pollution resulting in acid rain in both the US and Canada |
| Exclusive economic zone | 11,351,000 km2 (4,383,000 sq mi) |
The term "United States," when used in the geographic sense, refers to thecontiguous United States (sometimes referred to as theLower 48, including theDistrict of Columbia not as a state),Alaska,Hawaii, the fiveinsularterritories ofPuerto Rico,Northern Mariana Islands,U.S. Virgin Islands,Guam,American Samoa, andminor outlying possessions.[1] The United States shares land borders withCanada andMexico andmaritime borders withRussia,Cuba,the Bahamas, and many other countries, mainly in the Caribbean[note 2]in addition toCanada andMexico. Thenorthern border of the United States with Canada is the world's longest bi-national land border.
The state ofHawaii isphysiographically andethnologically part of thePolynesian subregion ofOceania.[7] U.S. territories are located in thePacific Ocean and theCaribbean.
From 1989 through 1996, the total area of the US was listed as 9,372,610 km2 (3,618,780 sq mi) (land and inland water only). The listed total area changed to 9,629,091 km2 (3,717,813 sq mi) in 1997 (Great Lakes area and coastal waters added), to 9,631,418 km2 (3,718,711 sq mi) in 2004, to 9,631,420 km2 (3,718,710 sq mi) in 2006, and to 9,826,630 km2 (3,794,080 sq mi) in 2007 (territorial waters added). Currently, the CIAWorld Factbook gives 9,826,675 km2 (3,794,100 sq mi),[8] theUnited Nations Statistics Division gives 9,629,091 km2 (3,717,813 sq mi),[9] and theEncyclopedia Britannica gives 9,522,055 km2 (3,676,486 sq mi) (Great Lakes area included but not coastal waters).[10] These sources consider only the 50 states and the Federal District and exclude overseas territories. The US has the 2nd largestExclusive Economic Zone of 11,351,000 km2 (4,383,000 sq mi).
Bytotal area (water as well as land), the United States is either slightly larger or smaller than thePeople's Republic of China, making it the world's third or fourth-largest country.[11] Both countries are smaller thanRussia andCanada in total area but are larger thanBrazil. By land area only (exclusive of waters), the United States is the world's third largest country, after Russia and China, with Canada in fourth. Whether the US or China is the third largest country by total area depends on two factors: (1) the validity of China's claim onAksai Chin andTrans-Karakoram Tract (both these territories are also claimed by India, so are not counted); and (2) how the US calculates its surface area. Since the initial publishing of the World Factbook, the CIA has updated the total area of the United States several times.[12]
The United States shares land borders with Canada to the north andMexico to the south, aterritorial water border with Russia in the northwest, and two territorial water borders in the southeast betweenFlorida andCuba, and Florida andthe Bahamas. The contiguous 48 states are otherwise bounded by thePacific Ocean on the west, theAtlantic Ocean on the east, and theGulf of Mexico to the southeast.Alaska borders the Pacific Ocean to the south and southwest, theBering Strait to the west, and theArctic Ocean to the north;Hawaii lies far to the southwest of the mainland in the Pacific Ocean.
Forty-eight of the states are in the single region between Canada and Mexico. This group is referred to, with varying precision and formality, as thecontiguous United States, and as the "Lower 48". Alaska, which is included in the term "continental United States", is located at the northwestern end ofNorth America.
The nation's capital city,Washington, D.C., was established in 1800 after being relocated there fromPhiladelphia. It was established as a federal district located on land donated by the state ofMaryland;Virginia also donated land, but it was returned in 1849. The United States also hasoverseas territories with varying levels of autonomy and organization, including theCaribbean territories ofPuerto Rico and theU.S. Virgin Islands, formerly known as the Danish Virgin Islands and purchased by the United States at the beginning ofWorld War II, the Pacific territories ofAmerican Samoa,Guam and theNorthern Mariana Islands, and severaluninhabited island territories. Some of the territories acquired were part of theterritorial evolution of the United States or a product of the nation's effort to gain access to the east.
Nearly all of the United States is in theNorthern Hemisphere with the exception ofAmerican Samoa andJarvis Island.[13]
Within the continental U.S. there areeight distinct physiographic divisions.[14] These major divisions are:
Theeastern United States has a varied topography. A broad, flat coastal plain lines the Atlantic and Gulf shores from the Texas-Mexico border toNew York City, and includes the Florida peninsula. This broad coastal plain andbarrier islands make up the widest and longest beaches in the United States, much of it composed of soft, white sands. TheFlorida Keys are a string ofcoral islands that reach the southernmost city on the United States mainland atKey West inSouth Florida.
Areas further inland feature rolling hills, mountains, and a diverse collection of temperate and subtropical moist and wet forests. Parts of interior Florida and South Carolina are also home tosandhill communities. TheAppalachian Mountains form a line of low mountains separating the eastern seaboard from theGreat Lakes and theMississippi basins.New England features rocky seacoasts and rugged mountains with peaks up to 6,200 feet and valleys dotted with rivers and streams. Offshore islands dot the Atlantic and Gulf coasts. A recent global remote sensing analysis suggested that there were 6,622 km2 oftidal flats in the United States, making it the 4th ranked country in terms of tidal flat area.[15]
The fiveGreat Lakes are located in the north-central portion of the country, four of them forming part of the border with Canada; onlyLake Michigan is situated entirely within the United States. Thesoutheast United States, generally stretching from theOhio River southwards, includes a variety of warm temperate and subtropical moist and wet forests, as well as warm temperate and subtropical dry forests nearer theGreat Plains in the west of the region. West of the Appalachians lies the lush Mississippi River basin and two large eastern tributaries, the Ohio River and theTennessee River. The Ohio andTennessee valleys and theMidwest consist largely of rolling hills, interior highlands and small mountains, jungle-like marsh and swampland near the Ohio River, and productive farmland, stretching south to theGulf Coast. The Midwest also has a vast amount of cave systems.
The Great Plains lie west of the Mississippi River and east of theRocky Mountains. A large portion of the country's agricultural products are grown in the Great Plains. Before their general conversion to farmland, the Great Plains were noted for their extensive grasslands, fromtallgrass prairie in the eastern plains toshortgrass steppe in the westernHigh Plains. Elevation rises gradually from less than a few hundred feet near the Mississippi River to more than a mile high in the High Plains. The generally low relief of the plains is broken in several places, most notably in theOzark andOuachita Mountains, which form theU.S. Interior Highlands, the only major mountainous region between the Rocky Mountains and the Appalachian Mountains.[16][17]
The Great Plains come to an abrupt end at the Rocky Mountains. The Rocky Mountains form a large portion of theWestern U.S., entering from Canada and stretching nearly to Mexico. The Rocky Mountain region is the highest region of the United States by average elevation. The Rocky Mountains generally contain fairly mild slopes and wider peaks compared to some of the other great mountain ranges, with a few exceptions, including theTeton Range inWyoming and theSawatch Range inColorado. The highest peaks of the Rockies are found in Colorado, the tallest peak beingMount Elbert at 14,440 ft (4,400 m). Instead of being one generally continuous and solid mountain range, it is broken up into several smaller intermittent mountain ranges, forming a large series of basins and valleys.
West of the Rocky Mountains lies theIntermontane Plateaus, also known as theIntermountain West, a large, arid desert lying between the Rockies and theCascades andSierra Nevada ranges. The large southern portion, known as theGreat Basin, consists of salt flats, drainage basins, and many small north–south mountain ranges. TheSouthwest is predominantly a low-lying desert region. A portion known as theColorado Plateau, centered around theFour Corners region, is considered to have some of the most spectacular scenery in the world. It is accentuated in such national parks asGrand Canyon,Arches,Mesa Verde andBryce Canyon, among others. Other smaller Intermontane areas include theColumbia Plateau, which covers easternWashington state, westernIdaho and northeastOregon and theSnake River Plain in southern Idaho.
The Intermontane Plateaus come to an end at the Cascade Range and the Sierra Nevada. The Cascades consist of largely intermittent, volcanic mountains, many rising prominently from the surrounding landscape. The Sierra Nevada, further south, is a high, rugged, and dense mountain range. It contains the highest point in the contiguous 48 states,Mount Whitney (14,505 ft or 4,421 m). It is located at the boundary betweenCalifornia'sInyo andTulare counties, just 84.6 mi or 136.2 km west-northwest of the lowest point in North America at theBadwater Basin inDeath Valley National Park at 279 ft or 85 m below sea level.[18] These areas contain some spectacular scenery as well, as evidenced by such national parks asYosemite andMount Rainier. West of the Cascades and Sierra Nevada is a series of valleys, such as theCentral Valley in California and theWillamette Valley in Oregon. Along the coast is a series of low mountain ranges known as thePacific Coast Ranges.
Alaska contains some of the most dramatic scenery in the country. Tall, prominent mountain ranges rise up sharply from broad, flat tundra plains. On the islands off the south and southwest coast are many volcanoes. Hawaii, far to the south of Alaska in the Pacific Ocean, is a chain of tropical,volcanic islands, popular as a tourist destination for many fromEast Asia and the mainland United States.
The territories of Puerto Rico and the U.S. Virgin Islands encompass a number of tropical isles in the northeasternCaribbean Sea. In the Pacific Ocean the territories of Guam and the Northern Mariana Islands occupy the limestone and volcanic isles of the Mariana archipelago, and American Samoa (the only populated US territory in the southern hemisphere) encompasses volcanic peaks and coral atolls in the eastern part of theSamoan Islands chain.[note 3]
The Atlantic coast of the United States is low, with minor exceptions. The Appalachian Highland owes its oblique northeast–southwest trend tocrustal deformations which in very early geological time gave a beginning to what later came to be the Appalachian Mountain system. This system had its climax of deformation so long ago (probably inPermian time) that it has since then been very generally reduced to moderate or lowrelief. It owes its present-day altitude either to renewed elevations along the earlier lines or to the survival of the most resistant rocks as residual mountains. The oblique trend of this coast would be even more pronounced but for a comparatively modern crustal movement, causing a depression in the northeast resulting in an encroachment of the sea upon the land. Additionally, the southeastern section has undergone an elevation resulting in the advance of the land upon the sea.
While the Atlantic coast is relatively low, the Pacific coast is, with few exceptions, hilly or mountainous. This coast has been defined chiefly by geologically recent crustal deformations, and hence still preserves a greater relief than that of the Atlantic. The low Atlantic coast and the hilly or mountainous Pacific coast foreshadow the leading features in the distribution of mountains within the United States.
The east coast Appalachian system, originally forest covered, is relatively low and narrow and is bordered on the southeast and south by an important coastal plain. TheCordilleran system on the western side of the continent is lofty, broad and complicated, having two branches, the Rocky Mountain System and the Pacific Mountain System. In between these mountain systems lie theIntermontane Plateaus. Both theColumbia River andColorado River rise far inland near the easternmost members of the Cordilleran system, and flow through plateaus and intermontane basins to the ocean. Heavy forests cover the northwest coast, but elsewhere trees are found only on the higher ranges below the Alpine region. The intermontane valleys, plateaus and basins range from treeless to desert with the most arid region being in the southwest.
Elevation extremes:
Due to its large size and wide range of geographic features, the United States contains examples of nearly every global climate. The climate is subtropical in theSouthern United States,continental in the north, tropical inHawaii and southernFlorida, polar in Alaska, semiarid in the Great Plains west of the100th meridian, Mediterranean in coastalCalifornia and arid in theGreat Basin and theSouthwest. Its comparatively favorable agricultural climate contributed (in part) to the country's rise as a world power, with infrequent severe drought in the major agricultural regions, a general lack of widespread flooding, and a mainly temperate climate that receives adequate precipitation.
The main influence on U.S. weather is thepolar jet stream which migrates northward into Canada in the summer months, and then southward into the US in the winter months. The jet stream brings in large low-pressure systems from the northernPacific Ocean that enters the US mainland over the Pacific Northwest. TheCascade Range,Sierra Nevada, andRocky Mountains pick up most of the moisture from these systems as they move eastward via theorographic effect, and they are greatly diminished by the time they reach the High Plains.
Once they move over the Great Plains, uninterrupted flat land allows them to reorganize and can lead to major clashes of air masses. In addition, moisture from theGulf of Mexico is often drawn northward. When combined with a powerful jet stream, this can lead to violent thunderstorms, especially during spring and summer. Sometimes during winter, these storms can combine with another low-pressure system as they move up the East Coast and into theAtlantic Ocean, where they intensify rapidly.These storms are known asNor'easters and often bring widespread, heavy rain, wind, and snowfall toNew England. The uninterrupted grasslands of the Great Plains also lead to some of the most extreme climate swings in the world. Temperatures can rise or drop rapidly, winds can be extreme, and the flow of heat waves or Arctic air masses often advance uninterrupted through the plains.
TheGreat Basin andColumbia Plateau (theIntermontane Plateaus) are arid or semiarid regions that lie in the rain shadow of theCascades andSierra Nevada. Precipitation averages less than 15 inches (38 cm). The Southwest is a hot desert, with temperatures exceeding 100 °F (37.8 °C) for several weeks at a time in summer. The Southwest and the Great Basin are also affected by themonsoon from theGulf of California from July to September, which brings localized but often severe thunderstorms to the region.
Much of California consists of aMediterranean climate, with sometimes excessive rainfall from October–April and nearly no rain the rest of the year. In thePacific Northwest rain falls year-round but is much heavier during winter and spring. The mountains of the west receive abundant precipitation and very heavy snowfall. The Cascades are one of the snowiest places in the world, with some places averaging over 600 inches (1,524 cm) of snow annually, but the lower elevations closer to the coast receive very little snow.
Florida has asubtropical climate in the northern part of the state and atropical climate in the southern part of the state. Summers are wet and winters are dry in Florida. Annually, much of Florida and the deep southern states is frost-free. The mild winters of Florida allow a massive tropical fruit industry to thrive in the central part of the state, making the US second to only Brazil incitrus production worldwide.
Another significant (but localized) weather effect islake-effect snow that falls south and east of theGreat Lakes, especially in the hilly portions of theUpper Peninsula ofMichigan and on theTug Hill Plateau inNew York. The lake effect dumped well over 5 feet (1.52 m) of snow in the area of Buffalo, New York throughout the 2006–2007 winter. TheWasatch Front andWasatch Range inUtah can also receive significant lake effect accumulations from theGreat Salt Lake.
In northernAlaska,tundra andarctic conditions predominate, and the temperature has fallen as low as −80 °F (−62.2 °C).[20] On the other end of the spectrum,Death Valley, California once reached 134 °F (56.7 °C), the highest temperature ever recorded on Earth.[21][22]
On average, the mountains of the western states receive the highest levels of snowfall on Earth. The greatest annual snowfall level is atMount Rainier inWashington, at 692 inches (1,758 cm); the record there was 1,122 inches (2,850 cm) in the winter of 1971–72. This record was broken by the Mt. Baker Ski Area in northwestern Washington which reported 1,140 inches (2,896 cm) of snowfall for the 1998–99 snowfall season. Other places with significant snowfall outside the Cascade Range are theWasatch Mountains inUtah, theSan Juan Mountains inColorado, and theSierra Nevada inCalifornia.
In the east, the region near the Great Lakes and the mountains of the Northeast receive the most snowfall, although they do not near snowfall levels in the western United States. Along the northwestern Pacific coast, rainfall is greater than anywhere else in the continental U.S., withQuinault Rainforest in Washington having an average of 137 inches (348 cm).[23] Hawaii receives even more, with 404 inches (1,026 cm) measured annually in theBig Bog, inMaui.[24]Pago Pago Harbor inAmerican Samoa is the rainiest harbor in the world (because of the 523 meterRainmaker Mountain).[19] TheMojave Desert, in the southwest, is home to the driest locale in the U.S.Yuma, Arizona, has an average of 2.63 inches (6.7 cm) ofprecipitation each year.[25]
In central portions of the U.S.,tornadoes are more common than anywhere else on Earth[26] and touch down most commonly in the spring and summer. Deadly and destructivehurricanes occur almost every year along the Atlantic seaboard and the Gulf of Mexico. The Appalachian region and the Midwest experience the worst floods, though virtually no area in the U.S. is immune to flooding. The Southwest has the worst droughts; one is thought to have lasted over 500 years and to have hurtAncestral Pueblo peoples.[27] The West is affected by large wildfires each year.
The United States is affected by a variety ofnatural disasters yearly. Although drought is rare, it has occasionally caused major disruption, such as during theDust Bowl (1931–1942). Farmland failed throughout the Plains, entire regions were substantially depopulated, and dust storms ravaged the land.
According to a 2023 Gallup survey, around one in three Americans said that they directly experienced a severe weather condition over the previous two years.[28] The Great Plains and Midwest, due to the contrasting air masses, see frequent severe thunderstorms and tornado outbreaks during spring and summer with around 1,000 tornadoes occurring each year.[29] The strip of land from northTexas north toKansas andNebraska and east intoTennessee is known asTornado Alley, where many houses have tornado shelters and many towns have tornado sirens, due to the very frequent tornado formation in the region.
Hurricanes are another natural disaster found in the US, which can hit anywhere along theGulf Coast or theAtlantic Coast as well as Hawaii in the Pacific Ocean. Particularly at risk are the central and southernTexas coasts, the area from southeasternLouisiana east to theFlorida Panhandle, peninsularFlorida, and theOuter Banks ofNorth Carolina, although any portion of the coast could be struck. TheU.S. territories and possessions in theCaribbean, includingPuerto Rico and theU.S. Virgin Islands, are also vulnerable to hurricanes due to their location in theCaribbean Sea.
Hurricane season runs from June 1 to November 30, with a peak from mid-August through early October. Some of the more devastating hurricanes have included theGalveston Hurricane of 1900,Hurricane Andrew in 1992,Hurricane Katrina in 2005, andHurricane Harvey andHurricane Maria in 2017.
Hurricanes (known as cyclones in the Pacific Ocean) fail to make landfall on the Pacific Coast of the United States due to water temperatures being too cool to sustain them. However, the remnants of tropical cyclones from the Eastern Pacific occasionally impact the western United States, bringing moderate to heavy rainfall.
Occasional severe flooding is experienced in the United States. Significant floods throughout history include theGreat Mississippi Flood of 1927, theGreat Flood of 1993, and widespread flooding and mudslides caused by the 1982–83El Niño event in the western United States. Flooding is still prevalent, mostly on the Eastern Coast, during hurricanes or other inclement weather, for example in 2012, whenHurricane Sandy devastated the region. Localized flooding can, however, occur anywhere, and mudslides from heavy rain can cause problems in any mountainous area, particularly the Southwest. Large stretches of desert shrub in the west can fuel the spread ofwildfires. The narrow canyons of many mountain areas in the west and severe thunderstorm activity during the summer lead toflash floods as well, which can sometimes be devastating, whilenor'easter snowstorms can bring activity to a halt throughout the Northeast (although heavy snowstorms can occur almost anywhere).
The West Coast of the continental United States makes up part of thePacific Ring of Fire, an area of heavy tectonic and volcanic activity that is the source of 90% of the world's earthquakes.[30] The American Northwest sees the highest concentration of active volcanoes in the United States, inWashington,Oregon andnorthern California along theCascade Mountains. There are several active volcanoes located in the islands of Hawaii, including Kilauea in ongoing eruption since 1983, but they do not typically adversely affect the inhabitants of the islands. There has not been a major life-threatening eruption on the Hawaiian Islands since the 17th century. Volcanic eruptions can occasionally be devastating, such as in the1980 eruption of Mount St. Helens in Washington.
The Ring of Fire makesCalifornia and southernAlaska particularly vulnerable toearthquakes. Earthquakes can cause extensive damage, such as the1906 San Francisco earthquake or the 1964Good Friday earthquake nearAnchorage, Alaska. California is well known for seismic activity and requires large structures to beearthquake resistant to minimize loss of life and property.[31] Outside of devastating earthquakes, California experiences minor earthquakes on a regular basis.
There have been about 100 significant earthquakes annually from 2010 to 2012. Past averages were 21 a year. This is believed to be due to the deep disposal of wastewater fromfracking. None have exceeded a magnitude of 5.6, and no one has been killed.[32]
Other natural disasters includetsunamis around the Pacific Basin, mudslides in California, and forest fires in the western half of the contiguous U.S. Although drought is relatively rare, it has occasionally caused major economic and social disruption, such as during theDust Bowl (1931–1942), which resulted in widespread crop failures and dust storms, beginning in the southern Great Plains and reaching to the Atlantic Ocean.
According to report by U.S.Census Bureau, in 2022 natural disasters led to the forced displacement of 3.3 million people, more than 1.3% of the U.S. adult population, with half of the displacements being caused by thehurricanes. The survey-report stated that inFlorida, the devastation caused by Hurricanes Ian and Nicole resulted in the relocation of around 1 million people, or about one in every 17 adult residents. InLouisiana, where inhabitants were still dealing with the devastating results ofHurricane Ida the year before, more than 409,000 people, or almost one in every eight residents, were moved. Despite this, theLouisiana state saw a relatively calm hurricane season in 2022.[33]
The United States holds many areas for the use and enjoyment of the public. These includenational parks,national monuments,national forests,wilderness areas, and other areas. For lists of areas, see the following articles:
In terms ofhuman geography, the United States is inhabited by adiverse set of ethnicities and cultures.
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