The United States of America is a federal republic primarily located in North America, consisting of fifty states and the federal capital district of Washington, D.C. The forty-eight contiguous states share borders with Canada to the north and Mexico to the south, while Alaska occupies a semi-exclave in the northwest and Hawaii forms an archipelago in the Pacific Ocean. The nation also asserts sovereignty over five major island territories and various uninhabited islands in Oceania and the Caribbean, establishing it as a megadiverse country with the world's third-largest land area.

Paleo-Indians migrated from North Asia to North America at least 15,000 years ago, forming diverse civilizations before European discovery began in 1492. British colonization started with the 1607 settlement of Virginia, leading to the Thirteen Colonies where the American Enlightenment valued republicanism and liberalism. Clashes with the British Crown over taxation led to the American Revolution, resulting in the Declaration of Independence on July 4, 1776. Victory in the Revolutionary War brought international recognition, followed by westward expansion and the Civil War, which abolished slavery after the Union's victory in 1865.

The country features vast uninhabited areas of natural beauty punctuated by cities ringed by sprawling suburbs. Notable landmarks include the skyscrapers of Manhattan and Chicago, the natural wonders of Yellowstone and Alaska, and the canyonlands of the Southwest. The Pacific Northwest offers towering volcanoes and rugged coastlines, while Florida, Hawaii, and Southern California provide warm, sunny beaches. The geography spans a continent and numerous islands, creating a wide array of tourist destinations that define the nation's physical character.

Shaped by centuries of immigration, the culture is diverse and globally influential, often described as a melting pot of cultures from around the world. The U.S. plays a dominant role in the global cultural landscape, with its landmarks and landscapes featured in countless books, movies, and television programs. Major cities offer distinct experiences, such as the colonial history of Boston, the film industry of Los Angeles, and the vibrant Latin-influenced Caribbean culture of Miami. New Orleans is known for jazz and Mardi Gras, while New York City attracts visitors with world-class arts and architecture.

The population was 340,110,988 as of 2024, though the source notes it exceeds 341 million. The economy has been the world's largest since about 1890, accounting for over a quarter of nominal global GDP, and the nation ranks high in economic competitiveness and innovation. It is widely considered to have the most powerful armed forces in the world and plays a major role in global political, cultural, economic, and military affairs through membership in organizations like the United Nations Security Council.