The United States of America is a federal republic consisting of 50 states and a federal district. The country covers an area of about 3,000,000 square miles, making it the world’s third largest country by land area.The United States has a population of almost 300 million people, making it the world’s most populous nation. English is the official language of the United States, but over 60 other languages are spoken in the country. The United States Constitution was signed on September 17, 1787 and establishes the principles on which the country operates. The United States is a founding member of NATO, the United Nations, and the World Trade Organization.