United States of America

The United States of America is a country located mainly in North America, made up of 50 states, one federal district, five major unincorporated territories, nine minor outlying islands and 326 Indian reservations. The country's national capital is Washington, D.C., while New York City is its most populous city and main financial center. The first people of North America migrated from Siberia, crossed the Bering land bridge and arrived in what is now the United States some 12 000 years ago, but some evidence indicates an even earlier arrival date. As time passed, indigenous cultures in North America became more sophisticated, and some of them, such as the pre-Columbian Mississippian culture in the southeast, developed highly advanced agriculture, architecture and complex societies. The British colonization, which began in 1607, led to the founding of thirteen colonies in what is now the eastern United States. They conflicted with the British Crown, which led to the American Revolution and the subsequent Revolutionary War. On the fourth of July 1776, the United States declared its independence. The United States' main characteristic is probably its great diversity. The environment ranges from arctic to subtropical, from humid rainforest to arid desert, from rugged mountain top to flat prairie. While the United States has a large total population by world standards, it has relatively low overall population density. The country contains some of the world's largest urban concentrations, along with some of the most extensive, almost uninhabited areas.