9,826,675 sq km (3,794,100 sq miles).

324,118,787 (UN estimate 2016).

32.5 per sq km.

Washington, DC.

Federal republic.

Covering a large part of the North American continent, the USA shares borders with Canada to the north and Mexico to the south. The country has coasts on the Atlantic, Pacific and Arctic oceans, the Caribbean Sea and the Gulf of Mexico. The State of Alaska, in the northwest corner of the US, is not part of the continental US; it is separated from the rest of the USA by Canada. Similarly, Hawaii is not part of the 'lower 48' states; it lies in the central Pacific Ocean.

The country's dependent territories are offshore and have distinct geographies of their own; the majority are islands. The third-largest country in the world (after the Russian Federation and Canada), the USA has an enormous diversity of geographical features, including mountains, plains, and coastal zones. Though there are many cities that are densely populated with more manmade features than natural ones, there are also vast rural areas that are far more sparsely populated. The climate ranges from subtropical to arctic, with a corresponding breadth of flora and fauna. For a more detailed description of each region's geographical characteristics, see the individual state sections.

Nearly half of all Americans are Protestant with Roman Catholic, Mormon, Jewish and many ethnic minorities. An increasing percentage of Americans are distancing themselves from formal religious affiliations; more than 19% declared no affiliation in 2015.

Americans are renowned for their openness and friendliness to visitors.

Shaking hands is the usual form of greeting. A relaxed and informal atmosphere is usually the norm. As long as the fundamental rules of courtesy are observed, there need be no fear of offending anyone of any background. Gifts are appreciated if one is invited to a private home. As a rule, dress is casual. High-end restaurants, hotels and clubs may require more formal attire.

Smoking is increasingly unpopular in the US; it is essential to ask permission before lighting up. Smoking is not allowed on city transport and restricted or forbidden in public buildings in most states. An increasing number of states (including California and New York) have banned smoking altogether in many public places.

The wide variety of national origins and the USA's relatively short history has resulted in numerous cultural and traditional customs living alongside each other. In large cities, people of the same ethnic background often live within the same communities, although race relations remain fraught in certain regions, as highlighted by the Ferguson riots in 2014 and Baltimore protests in 2015.

120 volts AC, 60Hz. Plugs have two flat pins with or without a third round grounding pin.

President Donald Trump since 2017.

President Donald Trump since 2017.

Following the arrival of Christopher Columbus in North America in 1492, waves of European settlers, mainly English, French and Dutch, crossed the Atlantic and by the 17th century had colonised the Eastern Seaboard. The American War of Independence (1775–1783) ended colonial rule and by 1853, the boundaries of the mainland United States were, with the exception of Alaska, as they are today. Economic activity in the southern States centred on plantation agriculture where attempts to end slavery were fiercely opposed and the election of Lincoln to the presidency in 1861 resulted in the American Civil War as the southern States seceded from the Union. After four years of bloody fighting the more powerful Union forces prevailed and the country entered a period of consolidation, building up an industrial economy. The mid- and late-19th century also saw the development of foreign policy as formal links were established with the old colonial powers.

In Europe, US intervention in 1917 proved decisive for the Allies in WWI and signalled the emergence of the USA as a global power. Driven by free-market economics and innovative production methods the USA became the world’s leading economy. It entered WWII and by its end had developed nuclear weapons and the superpower conflict that dominated the late 20th century.

Its post-war foreign policy saw the US increase its global military presence, fighting in Korea, Vietnam and multiple interventions in the Middle East. Relations between the USA and the USSR improved greatly after 1985 under the new Gorbachev government.

In 1988, George Bush was elected to the White House as the Eastern Bloc collapsed and the Cold War thawed. He was followed by Bill Clinton who served two terms characterised by a growing economy before George W Bush won the 2000 presidential election in controversial circumstances and shaped a more aggressive and jingoistic US foreign policy, particularly after the terrorist attacks on the United States in 2001. In November 2008 a record turnout returned Barack Obama as the country’s first black president who also served two terms in the White House. In late 2016, businessman and television personality Donald Trump defeated Hilary Clinton to become the 45th president of the United States.

Did you know?

• The United States of America is made up of 50 states, the federal district of Washington, D.C., five major self-governing territories and a range of other assets.

• Famously called America’s only true art form, jazz grew out of the sounds and rhythms brought over by African slaves mixed with European folk traditions and popular songs.

• Among the inventions claimed by Americans are the telephone, the phonograph, the electric light bulb, the movie camera, the assembly line and the aeroplane.