The United States of America (USA), commonly referred to as the United States (US), America, or simply the States, is a federal republic consisting of 50 states, 16 territories, and a federal district. The 48 contiguous states and the federal district of Washington, D.C., are in central North America between Canada and Mexico. The state of Alaska is the northwestern part of North America and the state of Hawaii is an archipelago in the mid-Pacific. The country also has five populated and nine unpopulated territories in the Pacific and the Caribbean. At 3.79 million square miles (9.83 million km2) in total and with around 316 million people, the United States is the fourth-largest country by total area and third largest by population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The geography and climate of the United States is also extremely diverse, and it is home to a wide variety of wildlife.
Paleo-indians migrated from Asia to what is now the US mainland around 15,000 years ago, with European colonization beginning in the 16th century. The United States emerged from 13 British colonies located along the Atlantic seaboard. Disputes between Great Britain and these colonies led to the American Revolution. On July 4, 1776, delegates from the 13 colonies unanimously issued the Declaration of Independence. The ensuing war ended in 1783 with the recognition of independence of the United States from the Kingdom of Great Britain, and was the first successful war of independence against a European colonial empire. The current Constitution was adopted on September 17, 1787. The first 10 amendments, collectively named the Bill of Rights, were ratified in 1791 and guarantee many fundamental civil rights and freedoms.
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There are a number of areas in the 48 contiguous United States known informally as tri-state areas. A tri-state area is an area associated with a particular town or metropolis that lies across three states. Some, but not all, of these involve a state boundary tripoint.
Three other prominent areas that have been labeled tri-state areas are the the Chicago tri-state area, also known as Chicagoland, which includes Illinois, Indiana, and Wisconsin; theCincinnati tri-state area, including Ohio, Kentucky, and Indiana; and the Pittsburgh tri-state area, covering parts of Pennsylvania, Ohio, and West Virginia.
New York is a state in the Northeastern region of the United States. New York is the 27th-most extensive, the third-most populous, and the seventh-most densely populated of the 50 United States. New York is bordered by New Jersey and Pennsylvania to the south and by Connecticut, Massachusetts and Vermont to the east. The state has a maritime border with Rhode Island east of Long Island, as well as an international border with the Canadian provinces of Ontario to the west and north, and Quebec to the north. The state of New York is often referred to as New York State, so as to distinguish it from New York City.
New York City, with a Census-estimated population of over 8.3 million in 2012, is the most populous city in the United States. Alone, it makes up over 40 percent of the population of New York State. It is known for its status as a center for finance and culture and for its status as the largest gateway for immigration to the United States. New York City attracts considerably more foreign visitors than any other US city. Both the state and city were named for the 17th century Duke of York, future King James II of England.