Rail transport is a means of transferring of passengers and goods on wheeled vehicles running on rails known as tracks. It is commonly referred to as train transport. In contrast to road transport, where vehicles run on a prepared flat surface, rail vehicles are directionally guided by the tracks on which they run. Tracks consist of steel rails, installed on ties and ballast, on which the rolling stock fitted with metal wheels, moves. Other variations are possible, such as slab track, where the rails are fastened to a concrete foundation resting on a prepared subsurface. Rolling stock in a rail transport system encounters lower frictional resistance than road vehicles, so passenger and freight cars can be coupled into longer trains; the operation is carried out by a railway company, providing transport between train stations or freight customer facilities. Power is provided by locomotives which either draw electric power from a railway electrification system or produce their own power by diesel engines.
Most tracks are accompanied by a signalling system. Railways are a safe land transport system. Railway transport is capable of high levels of passenger and cargo utilization and energy efficiency, but is less flexible and more capital-intensive than road transport, when lower traffic levels are considered; the oldest known, man/animal-hauled railways date back to the 6th century BC in Greece. Rail transport commenced in mid 16th century in Germany in the form of horse-powered funiculars and wagonways. Modern rail transport commenced with the British development of the steam locomotives in the early 19th century, thus the railway system in Great Britain is the oldest in the world. Built by George Stephenson and his son Robert's company Robert Stephenson and Company, the Locomotion No. 1 is the first steam locomotive to carry passengers on a public rail line, the Stockton and Darlington Railway in 1825. George Stephenson built the first public inter-city railway line in the world to use only the steam locomotives all the time, the Liverpool and Manchester Railway which opened in 1830.
With steam engines, one could construct mainline railways, which were a key component of the Industrial Revolution. Railways reduced the costs of shipping, allowed for fewer lost goods, compared with water transport, which faced occasional sinking of ships; the change from canals to railways allowed for "national markets" in which prices varied little from city to city. The spread of the railway network and the use of railway timetables, led to the standardisation of time in Britain based on Greenwich Mean Time. Prior to this, major towns and cities varied their local time relative to GMT; the invention and development of the railway in the United Kingdom was one of the most important technological inventions of the 19th century. The world's first underground railway, the Metropolitan Railway, opened in 1863. In the 1880s, electrified trains were introduced, leading to electrification of tramways and rapid transit systems. Starting during the 1940s, the non-electrified railways in most countries had their steam locomotives replaced by diesel-electric locomotives, with the process being complete by the 2000s.
During the 1960s, electrified high-speed railway systems were introduced in Japan and in some other countries. Many countries are in the process of replacing diesel locomotives with electric locomotives due to environmental concerns, a notable example being Switzerland, which has electrified its network. Other forms of guided ground transport outside the traditional railway definitions, such as monorail or maglev, have been tried but have seen limited use. Following a decline after World War II due to competition from cars, rail transport has had a revival in recent decades due to road congestion and rising fuel prices, as well as governments investing in rail as a means of reducing CO2 emissions in the context of concerns about global warming; the history of rail transport began in the 6th century BC in Ancient Greece. It can be divided up into several discrete periods defined by the principal means of track material and motive power used. Evidence indicates that there was 6 to 8.5 km long Diolkos paved trackway, which transported boats across the Isthmus of Corinth in Greece from around 600 BC.
Wheeled vehicles pulled by men and animals ran in grooves in limestone, which provided the track element, preventing the wagons from leaving the intended route. The Diolkos was in use for over 650 years, until at least the 1st century AD; the paved trackways were later built in Roman Egypt. In 1515, Cardinal Matthäus Lang wrote a description of the Reisszug, a funicular railway at the Hohensalzburg Fortress in Austria; the line used wooden rails and a hemp haulage rope and was operated by human or animal power, through a treadwheel. The line still exists and is operational, although in updated form and is the oldest operational railway. Wagonways using wooden rails, hauled by horses, started appearing in the 1550s to facilitate the transport of ore tubs to and from mines, soon became popular in Europe; such an operation was illustrated in Germany in 1556 by Georgius Agricola in his work De re metallica. This line used "Hund" carts with unflanged wheels running on wooden planks and a vertical pin on the truck fitting into the gap between the planks to keep it going the right way.
The miners called the wagons Hunde from the noise. There are many references to their use in central Europe in the 16th century; such a transport system was used by German miners at Cal
World War II
World War II known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries; the major participants threw their entire economic and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China, it included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, the only use of nuclear weapons in war. Japan, which aimed to dominate Asia and the Pacific, was at war with China by 1937, though neither side had declared war on the other. World War II is said to have begun on 1 September 1939, with the invasion of Poland by Germany and subsequent declarations of war on Germany by France and the United Kingdom.
From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Finland and the Baltic states. Following the onset of campaigns in North Africa and East Africa, the fall of France in mid 1940, the war continued between the European Axis powers and the British Empire. War in the Balkans, the aerial Battle of Britain, the Blitz, the long Battle of the Atlantic followed. On 22 June 1941, the European Axis powers launched an invasion of the Soviet Union, opening the largest land theatre of war in history; this Eastern Front trapped most crucially the German Wehrmacht, into a war of attrition. In December 1941, Japan launched a surprise attack on the United States as well as European colonies in the Pacific. Following an immediate U. S. declaration of war against Japan, supported by one from Great Britain, the European Axis powers declared war on the U.
S. in solidarity with their Japanese ally. Rapid Japanese conquests over much of the Western Pacific ensued, perceived by many in Asia as liberation from Western dominance and resulting in the support of several armies from defeated territories; the Axis advance in the Pacific halted in 1942. Key setbacks in 1943, which included a series of German defeats on the Eastern Front, the Allied invasions of Sicily and Italy, Allied victories in the Pacific, cost the Axis its initiative and forced it into strategic retreat on all fronts. In 1944, the Western Allies invaded German-occupied France, while the Soviet Union regained its territorial losses and turned toward Germany and its allies. During 1944 and 1945 the Japanese suffered major reverses in mainland Asia in Central China, South China and Burma, while the Allies crippled the Japanese Navy and captured key Western Pacific islands; the war in Europe concluded with an invasion of Germany by the Western Allies and the Soviet Union, culminating in the capture of Berlin by Soviet troops, the suicide of Adolf Hitler and the German unconditional surrender on 8 May 1945.
Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender under its terms, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki on 6 and 9 August respectively. With an invasion of the Japanese archipelago imminent, the possibility of additional atomic bombings, the Soviet entry into the war against Japan and its invasion of Manchuria, Japan announced its intention to surrender on 15 August 1945, cementing total victory in Asia for the Allies. Tribunals were set up by fiat by the Allies and war crimes trials were conducted in the wake of the war both against the Germans and the Japanese. World War II changed the political social structure of the globe; the United Nations was established to foster international co-operation and prevent future conflicts. The Soviet Union and United States emerged as rival superpowers, setting the stage for the nearly half-century long Cold War. In the wake of European devastation, the influence of its great powers waned, triggering the decolonisation of Africa and Asia.
Most countries whose industries had been damaged moved towards economic expansion. Political integration in Europe, emerged as an effort to end pre-war enmities and create a common identity; the start of the war in Europe is held to be 1 September 1939, beginning with the German invasion of Poland. The dates for the beginning of war in the Pacific include the start of the Second Sino-Japanese War on 7 July 1937, or the Japanese invasion of Manchuria on 19 September 1931. Others follow the British historian A. J. P. Taylor, who held that the Sino-Japanese War and war in Europe and its colonies occurred and the two wars merged in 1941; this article uses the conventional dating. Other starting dates sometimes used for World War II include the Italian invasion of Abyssinia on 3 October 1935; the British historian Antony Beevor views the beginning of World War II as the Battles of Khalkhin Gol fought between Japan and the fo
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation include drizzle, sleet, snow and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and "precipitates", thus and mist are not precipitation but suspensions, because the water vapor does not condense sufficiently to precipitate. Two processes acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called "showers."Moisture, lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed into clouds and rain. This process is active when freezing rain occurs. A stationary front is present near the area of freezing rain and serves as the foci for forcing and rising air.
Provided necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely stratus and cumulonimbus. The cloud droplets will grow large enough to form raindrops and descend toward the Earth where they will freeze on contact with exposed objects. Where warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow is possible within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. On the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. Most precipitation is caused by convection; the movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah climes.
Precipitation is a major component of the water cycle, is responsible for depositing the fresh water on the planet. 505,000 cubic kilometres of water falls as precipitation each year. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres, but over land it is only 715 millimetres. Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Precipitation may occur on other celestial bodies, e.g. when it gets cold, Mars has precipitation which most takes the form of frost, rather than rain or snow. Precipitation is a major component of the water cycle, is responsible for depositing most of the fresh water on the planet. 505,000 km3 of water falls as precipitation each year, 398,000 km3 of it over the oceans. Given the Earth's surface area, that means the globally averaged annual precipitation is 990 millimetres. Mechanisms of producing precipitation include convective and orographic rainfall.
Convective processes involve strong vertical motions that can cause the overturning of the atmosphere in that location within an hour and cause heavy precipitation, while stratiform processes involve weaker upward motions and less intense precipitation. Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. Mixtures of different types of precipitation, including types in different categories, can fall simultaneously. Liquid forms of precipitation include drizzle. Rain or drizzle that freezes on contact within a subfreezing air mass is called "freezing rain" or "freezing drizzle". Frozen forms of precipitation include snow, ice needles, ice pellets and graupel; the dew point is the temperature to which a parcel must be cooled in order to become saturated, condenses to water. Water vapor begins to condense on condensation nuclei such as dust and salt in order to form clouds. An elevated portion of a frontal zone forces broad areas of lift, which form clouds decks such as altostratus or cirrostratus.
Stratus is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. It can form due to the lifting of advection fog during breezy conditions. There are four main mechanisms for cooling the air to its dew point: adiabatic cooling, conductive cooling, radiational cooling, evaporative cooling. Adiabatic cooling occurs when air expands; the air can rise due to convection, large-scale atmospheric motions, or a physical barrier such as a mountain. Conductive cooling occurs when the air comes into contact with a colder surface by being blown from one surface to another, for example from a liquid water surface to colder land. Radiational cooling occurs due to the emission of infrared radiation, either by the air or by the surface underneath. Evaporative cooling occurs when moisture is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature, or until it reaches saturation; the main ways water vapor is added to the air are: wind convergence into areas of upward motion, precipitation or virga falling from above, daytime heating evaporating water from the surface of oceans, water bodies or wet lan
1890 United States Census
The Eleventh United States Census was taken beginning June 2, 1890. It determined the resident population of the United States to be 62,979,766—an increase of 25.5 percent over the 50,189,209 persons enumerated during the 1880 census. The data was tabulated by machine for the first time; the data reported that the distribution of the population had resulted in the disappearance of the American frontier. Most of the 1890 census materials were destroyed in a 1921 fire and fragments of the US census population schedule exist only for the states of Alabama, Illinois, New Jersey, New York, North Carolina, South Dakota, Texas, the District of Columbia; this was the first census in which a majority of states recorded populations of over one million, as well as the first in which multiple cities – New York as of 1880, Philadelphia – recorded populations of over one million. The census saw Chicago rank as the nation's second-most populous city, a position it would hold until 1990, in which Los Angeles would supplant it.
The 1890 census collected the following information: The 1890 census was the first to be compiled using methods invented by Herman Hollerith and was overseen by Superintendents Robert P. Porter and Carroll D. Wright. Data was entered on a machine readable medium, punched cards, tabulated by machine; the net effect of the many changes from the 1880 census: the larger population, the number of data items to be collected, the Census Bureau headcount, the volume of scheduled publications, the use of Hollerith's electromechanical tabulators, was to reduce the time required to process the census from eight years for the 1880 census to six years for the 1890 census. The total population of 62,947,714, the family, or rough, was announced after only six weeks of processing; the public reaction to this tabulation was disbelief, as it was believed that the "right answer" was at least 75,000,000. The United States census of 1890 showed a total of 248,253 Native Americans living in the United States, down from 400,764 Native Americans identified in the census of 1850.
The 1890 census announced that the frontier region of the United States no longer existed, that the Census Bureau would no longer track the westward migration of the U. S. population. Up to and including the 1880 census, the country had a frontier of settlement. By 1890, isolated bodies of settlement had broken into the unsettled area to the extent that there was hardly a frontier line; this prompted Frederick Jackson Turner to develop his Frontier Thesis. The original data for the 1890 Census is no longer available. All the population schedules were damaged in a fire in the basement of the Commerce Building in Washington, D. C. in 1921. Some 25 % of the materials were presumed another 50 % damaged by smoke and water; the damage to the records led to an outcry for a permanent National Archives. In December 1932, following standard federal record-keeping procedures, the Chief Clerk of the Bureau of the Census sent the Librarian of Congress a list of papers to be destroyed, including the original 1890 census schedules.
The Librarian was asked by the Bureau to identify any records which should be retained for historical purposes, but the Librarian did not accept the census records. Congress authorized destruction of that list of records on February 21, 1933, the surviving original 1890 census records were destroyed by government order by 1934 or 1935; the other censuses for which some information has been lost are the 1810 enumerations. Few sets of microdata from the 1890 census survive, but aggregate data for small areas, together with compatible cartographic boundary files, can be downloaded from the National Historical Geographic Information System. Mayo-Smith, Richmond, "The Eleventh Census of the United States". In: The Economic Journal, Vol. 1, p. 43 - 58 1891 U. S Census Report Contains 1890 Census results Historical US Census data from the U. S. Census Bureau website Hollerith 1890 Census Tabulator by Columbia University "The Fate of the 1890 Population Census" from the National Archives website
A census is the procedure of systematically acquiring and recording information about the members of a given population. The term is used in connection with national population and housing censuses; the United Nations defines the essential features of population and housing censuses as "individual enumeration, universality within a defined territory and defined periodicity", recommends that population censuses be taken at least every 10 years. United Nations recommendations cover census topics to be collected, official definitions and other useful information to co-ordinate international practice; the word is of Latin origin: during the Roman Republic, the census was a list that kept track of all adult males fit for military service. The modern census is essential to international comparisons of any kind of statistics, censuses collect data on many attributes of a population, not just how many people there are. Censuses began as the only method of collecting national demographic data, are now part of a larger system of different surveys.
Although population estimates remain an important function of a census, including the geographic distribution of the population, statistics can be produced about combinations of attributes e.g. education by age and sex in different regions. Current administrative data systems allow for other approaches to enumeration with the same level of detail but raise concerns about privacy and the possibility of biasing estimates. A census can be contrasted with sampling in which information is obtained only from a subset of a population. Modern census data are used for research, business marketing, planning, as a baseline for designing sample surveys by providing a sampling frame such as an address register. Census counts are necessary to adjust samples to be representative of a population by weighting them as is common in opinion polling. Stratification requires knowledge of the relative sizes of different population strata which can be derived from census enumerations. In some countries, the census provides the official counts used to apportion the number of elected representatives to regions.
In many cases, a chosen random sample can provide more accurate information than attempts to get a population census. A census is construed as the opposite of a sample as its intent is to count everyone in a population rather than a fraction. However, population censuses rely on a sampling frame to count the population; this is the only way to be sure that everyone has been included as otherwise those not responding would not be followed up on and individuals could be missed. The fundamental premise of a census is that the population is not known and a new estimate is to be made by the analysis of primary data; the use of a sampling frame is counterintuitive as it suggests that the population size is known. However, a census is used to collect attribute data on the individuals in the nation; this process of sampling marks the difference between historical census, a house to house process or the product of an imperial decree, the modern statistical project. The sampling frame used by census is always an address register.
Thus it is not known how many people there are in each household. Depending on the mode of enumeration, a form is sent to the householder, an enumerator calls, or administrative records for the dwelling are accessed; as a preliminary to the dispatch of forms, census workers will check any address problems on the ground. While it may seem straightforward to use the postal service file for this purpose, this can be out of date and some dwellings may contain a number of independent households. A particular problem is what are termed'communal establishments' which category includes student residences, religious orders, homes for the elderly, people in prisons etc; as these are not enumerated by a single householder, they are treated differently and visited by special teams of census workers to ensure they are classified appropriately. Individuals are counted within households and information is collected about the household structure and the housing. For this reason international documents refer to censuses of housing.
The census response is made by a household, indicating details of individuals resident there. An important aspect of census enumerations is determining which individuals can be counted from which cannot be counted. Broadly, three definitions can be used: de facto residence; this is important to consider individuals who have temporary addresses. Every person should be identified uniquely as resident in one place but where they happen to be on Census Day, their de facto residence, may not be the best place to count them. Where an individual uses services may be more useful and this is at their usual, or de jure, residence. An individual may be represented at a permanent address a family home for students or long term migrants, it is necessary to have a precise definition of residence to decide whether visitors to a country should be included in the population count. This is becoming more important as students travel abroad for education for a period of several years. Other groups causing problems of enumeration are new born babies, people away on holiday, people moving home around census day, people without a fixed address.
People having second homes because of working in another part of the country or retaining a holiday cottage are dif
A semi-arid climate or steppe climate is the climate of a region that receives precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-arid climates, depending on variables such as temperature, they give rise to different biomes. A more precise definition is given by the Köppen climate classification, which treats steppe climates as intermediates between desert climates and humid climates in ecological characteristics and agricultural potential. Semi-arid climates tend to support short or scrubby vegetation and are dominated by either grasses or shrubs. To determine if a location has a semi-arid climate, the precipitation threshold must first be determined. Finding the precipitation threshold involves first multiplying the average annual temperature in °C by 20 adding 280 if 70% or more of the total precipitation is in the high-sun half of the year, or 140 if 30%–70% of the total precipitation is received during the applicable period, or 0 if less than 30% of the total precipitation is so received.
If the area's annual precipitation is less than the threshold but more than half the threshold, it is classified as a BS. Furthermore, to delineate "hot semi-arid climates" from "cold semi-arid climates", there are three used isotherms: Either a mean annual temperature of 18°C, or a mean temperature of 0°C or −3°C in the coldest month, so that a location with a "BS" type climate with the appropriate temperature above whichever isotherm is being used is classified as "hot semi-arid", a location with the appropriate temperature below the given isotherm is classified as "cold semi-arid". Hot semi-arid climates tend to be located in the 20s and 30s latitudes of the in proximity to regions with a tropical savanna or a humid subtropical climate; these climates tend to have hot, sometimes hot and warm to cool winters, with some to minimal precipitation. Hot semi-arid climates are most found around the fringes of subtropical deserts. Hot semi-arid climates are most found in Africa and South Asia. In Australia, a large portion of the Outback surrounding the central desert regions lies within the hot semi-arid climate region.
In South Asia, both India and sections of Pakistan experiences the seasonal effects of monsoons and feature short but well-defined wet seasons, but is not sufficiently wet overall to qualify as a tropical savanna climate. Hot semi-arid climates can be found in Europe, parts of North America, such as in Mexico, areas of the Southwestern United States, sections of South America such as the sertão, the Gran Chaco, on the poleward side of the arid deserts, where they feature a Mediterranean precipitation pattern, with rainless summers and wetter winters. Cold semi-arid climates tend to be located in elevated portions of temperate zones bordering a humid continental climate or a Mediterranean climate, they are found in continental interiors some distance from large bodies of water. Cold semi-arid climates feature warm to hot dry summers, though their summers are not quite as hot as those of hot semi-arid climates. Unlike hot semi-arid climates, areas with cold semi-arid climates tend to have cold winters.
These areas see some snowfall during the winter, though snowfall is much lower than at locations at similar latitudes with more humid climates. Areas featuring cold semi-arid climates tend to have higher elevations than areas with hot semi-arid climates, tend to feature major temperature swings between day and night, sometimes by as much as 20 °C or more in that time frame; these large diurnal temperature variations are seen in hot semi-arid climates. Cold semi-arid climates at higher latitudes tend to have dry winters and wetter summers, while cold semi-arid climates at lower latitudes tend to have precipitation patterns more akin to subtropical climates, with dry summers wet winters, wetter springs and autumns. Cold semi-arid climates are most found in Asia and North America. However, they can be found in Northern Africa, South Africa, sections of South America and sections of interior southern Australia and New Zealand. In climate classification, three isotherms means that delineate between hot and cold semi-arid climates — the 18°C average annual temperature or that of the coldest month, the warm side of the isotherm of choice defining a BSh climate from the BSk on the cooler side.
As a result of this, some areas can have climates that are classified as hot or cold semi-arid depending on the isotherm used. One such location is San Diego, which has cool summers for the latitude due to prevailing winds off the ocean but mild winters. Continental climate Dust Bowl Goyder's Line Köppen climate classification Palliser's Triangle Ustic Wave height
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti