The United States of America (USA), commonly known as the United States (U.S.) or America, is a federal republic composed of 50 states, a political district, five major self-governing territories, and various possessions. At 3.8 million square kilometers (9.8 million km2) as well as over 325 million people, America is the world‘s third- or – fourth-largest nation by complete area along with also the third-most populous country. The capital is Washington, D.C., and the biggest city by population in New York City. Forty-eight states and even the capital’s national district are contiguous and located in North America involving Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east and throughout the Bering Strait from Russia into the west. The U.S. lands are sprinkled about the Pacific Ocean along with the Caribbean Sea, stretching across nine official period zones. The exceptionally diverse geography, climate, and wildlife of the United States of America make it among the planet’s 17 megadiverse countries.
Paleo-Indians migrated from Siberia into the North American mainland 15,000 years ago.European colonization began in the 16th century. America emerged from the thirteen British colonies established across the East Coast. Numerous disputes involving Great Britain and the colonies following the French and Indian War led to the American Revolution, which started in 1775, and also the following Declaration of Independence in 1776. The warfare finished in 1783 together with the United States becoming the first country to gain freedom from European electricity. The present constitution was adopted in 1788, with the first ten amendments, collectively called the Bill of, being ratified in 1791 to ensure several fundamental civil liberties. America embarked on a vigorous expansion across North America throughout the 19th century, getting new lands, displacing Native American tribes, also gradually admitting new countries till it spanned the continent from 1848. Throughout the second half of the 19th century, the Civil War led to the abolition of both captivity. By the close of the century, the United States had expanded into the Pacific Ocean, and its economy, driven in large part by the Industrial Revolution, started to soar. The Spanish–American War and World War I confirmed the country’s status as a global military power. The USA emerged from World War II as a international superpower, the first country to develop atomic weapons, the only country to use them in warfare, and a permanent member of this United Nations Security Council. Throughout the Cold War, the United States and also the Soviet Union competed from the Space Race, culminating with the 1969 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 an exceptionally developed nation, together with the world‘s largest market by nominal GDP and second-largest economy by PPP, accounting for approximately a quarter of global GDP. The U.S. market is mostly post-industrial, characterized by the dominance of solutions and knowledge-based activities, although the manufacturing sector remains the second-largest on the planet.Although its population is only 4.3% of the world total, the U.S. holds 33.4 percent of their entire wealth on the planet, the most significant share of global wealth concentrated in one nation. The United States ranks among the highest nations in many measures of socioeconomic functionality, including average wage, human development, per capita GDP, and productivity per individual. The U.S. is the leading army power in the world, making up a third of international military spending, and also is a leading political, cultural, along with scientific drive internationally.