The first documented use of the phrase "United States of America" is a letter from January 2, 1776. Stephen Moylan, a Continental Army aide to General George Washington, wrote to Joseph Reed, Washington's … 展开

The first inhabitants of North America migrated from Siberia across the Bering land bridge about 12,000 years ago; the Clovis culture, which appeared around 11,000 BC, is believed to be the first widespread culture in the Am… 展开

The United States is the world's third-largest country by total area behind Russia and Canada. The 48 contiguous states and the District of Columbia occupy a combined area of 3,119,885 square miles (8,080,470 km ). The … 展开

The United States is a federal republic of 50 states and a federal district, Washington, D.C. It also asserts sovereignty over five unincorporated territories and several uninhabited island possessions. The world's oldest surviving f… 展开