A country of central and northwest North America with coastlines on the Atlantic and Pacific oceans. It includes the noncontiguous states of Alaska and Hawaii and various island territories in the Caribbean Sea and Pacific Ocean . The area now occupied by the contiguous 48 states was originally inhabited by numerous Native American peoples and was colonized beginning in the 16th century by Spain , France , the Netherlands , and England . Great Britain eventually controlled most of the Atlantic coast and, after the French and Indian Wars (1754-1763), the Northwest Territory and Canada . The original Thirteen Colonies declared their independence from Great Britain in 1776 and formed a government under the Articles of Confederation in 1781, adopting (1787) a new constitution that went into effect after 1789. The nation soon began to expand westward. Growing tensions over the issue of Black slavery divided the country along geographic lines, sparking the secession of the South and the Civil War (1861-1865). The remainder of the 19th century was marked by increased westward expansion, industrialization, and the influx of millions of immigrants. The United States entered World War II after the Japanese attack (1941) on Pearl Harbor and emerged after the war as a world power. Washington , D.C. , is the capital and New York the largest city. Population: 293,000,000. People around the world are attracted to USA because of it's economy and living standards which makes international relocation and moving to USA a regular event.