The United States is a nation in the Western Hemisphere. It consists of forty-eight contiguous states on the North
American continent; Alaska, an enormous peninsula which forms the northwestern most part of North America,
and Hawaii, an archipelago in the Pacific Ocean. It also holds several United States territories in the Pacific &
Caribbean. The country shares land borders with Canada and Mexico and a water border with Russia.
|Relief map of the 48 states of the U.S. mainland
Geography of the United
Canada 5,526 miles
Mexico 2,067 miles
Coastlines 12,380 miles
Contiguous zone 24
nautical miles (44 km)
Economic zone 200
nautical miles (370 km)
Territorial sea 12 nautical
miles (22 km)
By total area including water, the United States is either slightly larger or smaller than the People's Republic of
China, making it the world's third or fourth largest country. Its rank depends on whether one includes two
territories claimed by India but governed by China when calculating China's size. Both China and the United
States follow behind Canada and Russia in total area. By land area (exclusive of waters), the United States is the
world's third largest country, following Russia and China. In total area, the United States is:
three-tenths the size of Africa (which is a continent-- not a nation)
half the size of South America (which is also a continent not a nation)
half the size of Russia
roughly the same size as China
slightly larger than Brazil
slightly more than one and a quarter times the size of Australia
two and a half times the size of Western Europe
roughly 14 times the size of France
roughly 39 times the size of the United Kingdom
Geography of the United
Total 3,717,813 sq mi
Land 3,536,294 sq mi
Water 181,519 sq mi
Latitude 38°0' N
|A satellite composite image of the contiguous United States. Deciduous vegetation and grasslands prevail in the east, transitioning to prairies, boreal forests, and the
Rockies in the west, and deserts in the southwest. In the northeast, the coasts of the Great Lakes and Atlantic seaboard host much of the country's population.
The United States shares land borders with Canada (to the north) and Mexico (to the south), and a territorial water border with Russia in the northwest. The contiguous forty-eight states are otherwise
bounded by the Pacific Ocean on the west, the Atlantic Ocean on the east, and the Gulf of Mexico to the southeast. Alaska borders the Pacific Ocean to the south, the Bering Strait to the west, and the
Arctic Ocean to the north, while 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 the continental or contiguous United States, and as the
Lower 48. Alaska, which is not included in the term contiguous United States, is at the northwestern end of North America, separated from the Lower 48 by Canada. The State of Hawaii is an
archipelago in the Pacific Ocean. The capital city, Washington, District of Columbia, is a federal district located on land donated by the state of Maryland. (Virginia had also donated land, but it was
returned in 1847.) The United States also have overseas territories with varying levels of independence and organization.
In total area (including inland water), Russia and Canada are larger than the United States. Ranking for third-largest status is disputed. Some sources (including Encyclopædia Britannica and all
publications of the People's Republic of China), list China as larger than the U.S. Many other sources list the U.S. as larger. The dispute appears to hinge on Taiwan, without which China takes fourth
place. Total U.S. area is 3,718,711 square miles (9,631,418 km²), of which land is 3,537,438 square miles (9,161,923 km²) and water is 181,273 square miles (469,495 km²). Ranked by land area, the
top countries in order are Russia, China, the U.S., and Canada.
The eastern United
States has a varied
topography. A broad, flat
coastal plain lines the
Atlantic and Gulf shores
from the Texas-Mexico
border to New York City,
and includes the Florida
peninsula. Areas further
inland feature rolling
hills and temperate
forests. The Appalachian
Mountains form a line of
separating the eastern
seaboard from the Great
Lakes and the
Mississippi Basin. The
five Great Lakes are
located in the
north-central portion of
the country, four of them
forming part of the
border with Canada. The
southeast United States
forests and, near the gulf
wetlands, especially in
Florida. West of the
Appalachians lies the
Mississippi River basin
and two large eastern
tributaries, the Ohio
River and the
Tennessee River. The
Ohio and Tennessee
Valleys and the Midwest
consist largely of rolling
hills and productive
south to the Gulf Coast.
The Great Plains lie west of the Mississippi River and east of the Rocky 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, from tallgrass prairie in the eastern plains to shortgrass steppe in the western High 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 the Ozark and Ouachita
Mountains, which form the U.S. Interior Highlands, the only major mountainous region between the Rocky Mountains and the Appalachian Mountains. The Great Plains come to an abrupt end at
the Rocky Mountains. The Rocky Mountains form a large portion of the Western U.S., entering from Canada and stretching nearly to Mexico. The Rocky Mountains generally contain fairly mild slopes
and low peaks compared to many of the other great mountain ranges, with a few exceptions (such as the Teton Mountains in Wyoming and the Sawatch Range in Colorado). In addition, instead of
being one generally continuous and solid mountain range, it is broken up into a number of smaller, intermittent mountain ranges, forming a large series of basins and valleys.
West of the Rocky Mountains lies the Intermontane Plateaus (also known as the Intermountain West), a large, arid desert lying between the Rockies and the Cascades and Sierra Nevada ranges. The
large southern portion, known as the Great Basin, consists of salt flats, drainage basins, and many small north-south mountain ranges. The Southwest is predominantly a low-lying desert region. A
portion known as the Colorado Plateau, centered around the Four Corners region, is considered to have some of the most spectacular scenery in the world. It is accentuated in such national parks as
Grand Canyon, Arches, and Bryce Canyon, among others.
|Mount McKinley, Alaska, the highest point in North America at 20,320 ft (6,194 m)
|The Grand Canyon from Moran Point. The Grand Canyon is among the most famous locations in the country.
The Intermontane Plateaus come to an end at the Cascade Range and the Sierra Nevada. The Cascades consist of largely intermittent, volcanic mountains 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; 4,421 m). These areas
contain some spectacular scenery as well, as evidenced by such national parks as Yosemite and Mount Rainier. West of the Cascades and Sierra Nevada is a series of valleys, such as the Central
Valley in California and the Willamette Valley in Oregon. Along the coast is a series of low mountain ranges known as the Pacific Coast Ranges. Much of the Pacific Northwest coast is inhabited by
some of the densest vegetation outside of the Tropics, and also the tallest trees in the world (the Redwoods).
Alaska contains some of the most dramatic and untapped 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 from East Asia and the
mainland United States.
The geography of the United States varies across their immense area. Within the contential U.S., eight distinct physiographic divisions exist, though each is composed of several smaller physiographic
subdivisions. These major divisions are:
Laurentian Upland - part of the Canadian Shield that extends into the northern United States Great Lakes area.
Atlantic Plain - the coastal regions of the eastern and southern parts includes the continental shelf, the Atlantic Coast and the Gulf Coast.
Appalachian Highlands - lying on the eastern side of the United States, it includes the Appalachian Mountains, Adirondacks and New England province.
Interior Plains - part of the interior contentintal United States, it includes much of what is called the Great Plains.
Interior Highlands - also part of the interior contentintal United States, this division includes the Ozark Plateau.
Rocky Mountain System - one branch of the Cordilleran system lying far inland in the western states.
Intermontane Plateaus - also divided into the Columbia Plateau, the Colorado Plateau and the Basin and Range Province, it is a system of plateaus, basins, ranges and gorges between the Rocky
and Pacific Mountain Systems. It is the setting for the Grand Canyon, the Great Basin and Death Valley.
Pacific Mountain System - the coastal mountain ranges and features in the west coast of the United States.
|Delicate Arch, Arches National Park, Utah
The Atlantic coast of the United States is, with minor exceptions, low. The
Appalachian Highland owes its oblique northeast-southwest trend to crustal
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 in Permian time) that it has since then been very
generally reduced to moderate or low relief. 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.
The following map, known as a physiographical map, shows geographical and
terrain information about the regions of the contiguous 48 states of the U.S. used by
earth scientists. The map indicates the age of the exposed surface as well as the
type of terrain. More information about the regions is covered in several sub articles
found in the additional topics subsection below.
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
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. The
Cordilleran 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, lie the Intermontaine Plateaus. 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 very arid region being in the southwest.
Both the Columbia River and Colorado River rise far inland near the easternmost
members of the Cordilleran system, and flow through plateaus and intermontaine
basins to the ocean.
The Laurentian Highlands, the Interior Plains and the Interior Highlands lie between
the two coasts, stretching from the Gulf of Mexico northward, far beyond the national
boundary, to the Arctic Ocean. The central plains are divided by a hardly perceptible
height of land into a Canadian and a United States portion. It is from the United
States side, that the great Mississippi system discharges southward to the Gulf of
Mexico. The upper Mississippi and some of the Ohio basin is the semi-arid prairie
region, with trees originally only along the watercourses. The uplands towards the
Appalachians were included in the great eastern forested area, while the western
part of the plains has so dry a climate that its native plant life is scanty, and in the
south it is practically barren.
See also: List of North American deserts
Lowest point: Death Valley, Inyo County, California 282 feet below sea level (-86 m)
Highest point: Mount McKinley, Denali Borough, Alaska 20,320 feet above sea level
|Physiographic Regions of the United States.
|Climate zones of the lower 48 United States.
Main article: Climate of the United States
Due to its large size and wide range of geographic features, the United States
contains examples of nearly every global climate. The climate is temperate in most
areas, tropical in Hawaii and southern Florida, polar in Alaska, semiarid in the Great
Plains west of the 100th meridian, Mediterranean in coastal California and arid in
the Great Basin. Its comparatively generous 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 the polar jet stream, which brings in large
low pressure systems from the northern Pacific Ocean. The Cascade Range, Sierra
Nevada, and Rocky Mountains pick up most of the moisture from these systems as
they move eastward. Greatly diminished by the time they reach the High Plains,
much of the moisture has been sapped by the orographic effect as it is forced over
several mountain ranges. However, once it moves over the Great Plains,
uninterrupted flat land allows it to reorganize and can lead to major clashes of air
masses. In addition, moisture from the Gulf 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 late winter and spring
these storms can combine with another low pressure system as they move up the
East Coast and into the Atlantic Ocean, where they intensify rapidly. These storms
are known as Nor'easters and often bring widespread, heavy snowfall to the
Mid-Atlantic and New England. The uninterrupted flat grasslands of the Great Plains
also leads to some of the most extreme climate swings in the world. Temperatures
can rise or drop rapidly and winds can be extreme, and the flow of heat waves or
Arctic air masses often advance uninterrupted through the plains.
The Great Basin and Columbia Plateau (the Intermontane Plateaus) are arid or
semiarid regions that lie in the rain shadow of the Cascades and Sierra Nevada.
Precipitation averages less than 15 inches (38 cm). The Southwest is a hot desert,
with temperatures exceeding 100°F (38°C) for several weeks at a time in summer.
The Southwest and the Great Basin are also affected by the monsoon from the Gulf
of California from July-September, which brings localized but often severe
thunderstorms to the region.
|Deep snow during the Blizzard of 2006 Nor'easter in Brooklyn, New York City.
|The U.S. State of Hawaii has a year-round tropical climate, and is known for its
many beaches, such as this one on O'ahu.
Much of California
consists of a
excessive rainfall from
October-April and nearly
no rain the rest of the
year. In the Pacific
Northwest rain falls
year-round, but is much
heavier during winter
and spring. The
mountains of the west
precipitation and very
heavy snowfall. The
Cascades are one of the
snowiest places in the
world, with some places
averaging over 600
inches (1,520 cm) of
snow annually, but the
lower elevations closer
to the coast receive very
little snow. Another
significant (but localized)
weather effect is
lake-effect snow that
falls south and east of
the Great Lakes,
especially in the hilly
portions of the Upper
Peninsula of Michigan
and on the Tug Hill
Plateau in New York.The
lake effect dumped well
over 5 feet of snow in the
Buffalo, New York area
2006-2007 winter The
Wasatch Front and
Wasatch Range in Utah
can also receive
significant lake effect
accumulations off of the
Great Salt Lake.
In northern Alaska, tundra and arctic conditions predominate, and the temperature
has fallen as low as minus 80 °F (−62 °C). On the other end of the spectrum,
Death Valley, California once reached 134 °F (56.7 °C), the second-highest
temperature ever recorded on Earth.
On average, the mountains of the western states receive the highest levels of
snowfall on Earth. The greatest annual snowfall level is at Mount Rainier in
Washington, at 692 inches (17,580 mm); the record there was 1,122 inches (28,500
mm) in the winter of 1971–72. This record was broken by the Mt. Baker Ski Area in
northwestern Washington which reported 1,140 inches of snowfall for the 1998-99
snowfall season. Other places with significant snowfall outside the Cascade Range
are the Wasatch Mountains, near the Great Salt Lake, and the Sierra Nevada, near
Lake Tahoe. In the east, while snowfall does not approach western levels, the
region near the Great Lakes and the mountains of the Northeast receive the most.
Along the northwestern Pacific coast, rainfall is greater than anywhere else in the
continental U.S., with Quinault Ranger in Washington having an average of 137
inches (3480 mm). Hawaii receives even more, with 460 inches (11,680 mm)
measured annually on Mount Waialeale, in Kauai. The Mojave Desert, in the
southwest, is home to the driest locale in the U.S. Yuma, Arizona, has an average of
2.63 inches (66.8 mm) of precipitation each year.
In central portions of the U.S., tornadoes are more common than anywhere else on
Earth and touch down most commonly in the spring and summer. Deadly and
destructive hurricanes 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
decimated the Anasazi people. The West is affected by large wildfires each year.
The United States is affected by a large variety of natural disasters yearly. Although
severe drought is rare, it has occasionally caused major problems, such as during
the Dust Bowl (1931-1942), which coincided with the Great Depression. Farmland
failed throughout the Plains, entire regions were virtually depopulated, and dust
storms ravaged the land. More recently, the western U.S. experienced widespread
drought from 1999-2004, and signs of a major, long-term drought across the Great
Plains have developed. In the past year, drought has spread from the Southern
Plains westward through the Southwest and east along the Gulf Coast to Florida.
|Size comparisons between the contiguous United States and other world geographic bodies
|A powerful tornado in Texas
The United States also experience, by a large margin, the most frequent and
powerful tornadoes in the world. The Great Plains and Midwest, due to the
contrasting air masses, sees frequent severe thunderstorms and tornado
outbreaks during spring and summer. The strip of land from north Texas north to
Kansas and east into Tennessee is known as Tornado Alley, where many houses
have tornado shelters and many towns have tornado sirens. Another natural
disaster that frequents the country are hurricanes, which can hit anywhere along the
Gulf Coast or the Atlantic Coast as well as Hawaii in the Pacific Ocean. Particularly
at risk are the central and southern Texas coasts, the area from southeastern
Louisiana east to the Florida Panhandle, the east coast of Florida, and the Outer
Banks of North Carolina, although any portion of the coast could be struck.
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 the
Galveston Hurricane of 1900, Hurricane Andrew in 1992, and Hurricane Katrina in
2005. The remnants of tropical cyclones from the Eastern Pacific also occasionally
impact the southwestern United States, bringing sometimes heavy rainfall.
|Total devastation in Gulfport, Mississippi following Hurricane Katrina in 2005.
Like drought, widespread severe flooding is rare. Some exceptions include the
Great Mississippi Flood of 1927, the Great Flood of 1993, and widespread flooding
and mudslides caused by the 1982-1983 El Niño event in the western United
States. 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 of
wildfires. The narrow canyons of many mountain areas in the west and severe
thunderstorm activity during the monsoon season in summer leads to sometimes
devastating flash floods as well, while Nor'Easter snowstorms can bring activity to a
halt throughout the Northeast (although heavy snowstorms can occur almost
The West Coast of the continental United States and areas of Alaska (including the Aleutian Islands, the Alaskan Peninsula and southern Alaskan coast) make up part of the Pacific Ring of Fire, an
area of heavy tectonic and volcanic activity that is the source of 90% of the world's earthquakes. The American Northwest sees the highest concentration of active volcanoes in the United States, in
Washington, Oregon and northern California along the Cascade 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 the 1980 eruption of Mount St. Helens in Washington.
The Ring of Fire makes California and southern Alaska particularly vulnerable to earthquakes. Earthquakes can cause extensive damage, such as the 1906 San Francisco Earthquake or the 1964
Good Friday Earthquake near Anchorage, Alaska. California is well known for seismic activity, and requires large structures to be earthquake resistant to minimize loss of life and property. Outside of
devastating earthquakes, California experiences minor earthquakes on a regular basis.
Natural hazards: tsunamis, volcanoes, and earthquake activity around Pacific Basin; hurricanes along the Atlantic and Gulf of Mexico coasts; tornadoes in the midwest and southeast; mud slides in
California; forest fires in the west; flooding; permafrost in northern Alaska, a major impediment to development; and on occasion a terrorist attack.
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