The United States of America (USA) is a federal republic located primarily in North America. It is a vast union comprising 50 states and a federal capital district, Washington, D.C. Geographically, the country stretches from the Atlantic Ocean to the Pacific Ocean, and from the Arctic Circle down to the Caribbean Sea. Its immense size gives it the world's third-largest land area and largest exclusive economic zone. The population is highly diverse, with major metropolitan areas like New York, Los Angeles, and Chicago serving as global economic and cultural hubs. The nation's economy is one of the largest and most diversified in the world.