Historically speaking, the United States has been a country of immigrants. Several native people lived in a huge land mass for centuries that now make the United States of America. Eventually, European settlers came in during the 17th century, followed by colonizers. United States had 13 colonies originally, all of which had their individual governments. Trouble started brewing when the British Government imposed tax on them but did not give representation in the Parliament. This led to the American Revolution (1775-1781) and on July 4, 1776 the American colonies adopted the Declaration of Independence. The American Constitution was adopted in 1778 and in 1779 George Washington became the first ever American President. After this, USA expanded westwards, grew considerably in size and was involved in several racial conflicts, the Civil War, World War II. Following this, its economy grew and today, the young nation has become the world's largest economy and is considered to be the most influential nation in the world. The country’s population is thoroughly diverse with people from all over the world moving here to find a better life.