The United States of America, commonly known as the United States (U.S.) or America, is a federal republic composed of fifty states, a federal district, five major self-governing territories, and various possessions.

Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico.

The state of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west.

The state of Hawaii is an archipelago in the mid-Pacific Ocean.

The U.S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine time zones.

The extremely diverse geography, climate and wildlife of the United States make it one of the world's seventeen megadiverse countries.

At 3.8 million square miles (9.8 million km2) and with over 324 million people, the United States is the world's third- or fourth-largest country by total area, third-largest by land area, and the third-most populous

It is one of the world's most ethnically diverse and multicultural nations, and is home to the world's largest immigrant population.

The capital is Washington, D.C., and the largest city is New York City; nine other major metropolitan areas—each with at least 4.5 million inhabitants—are Los Angeles, Chicago, Dallas, Houston, Philadelphia, Miami, Atlanta, Boston, and San Francisco.