The United States of America (USA), commonly referred to as the United States (U.S.) or America, is a federal republic composed of 50 states, a federal district, five major self-governing territories, and various possessions.[fn 1] The 48 contiguous states and federal district are in central North America between Canada and Mexico, with the state of Alaska in the northwestern part of North America and the state of Hawaii comprising an archipelago in the mid-Pacific. The territories are scattered about the Pacific Ocean and the Caribbean Sea.

Nine time zones are covered. The geography, climate and wildlife of the country are extremely diverse.

At 3.8 million square miles (9.8 million km2) and with over 324 million people, the United States is the world's third-largest country by total area (and fourth-largest by land area)[fn 2] and the third-most populous. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many other countries.

 Urbanization climbed to over 80% in 2010 and leads to growing megaregions. The country's capital is Washington, D.C. and its largest city is New York City; other major metropolitan areas include Los Angeles, Chicago, Dallas, San Francisco, Boston, Philadelphia, Houston, Atlanta, and Miami.

Sourse: wikipedia