The history of the United States dates back to the arrival of the first European settlers in the late 15th century and early 16th century. However, the United States as a unified nation came into being on July 4, 1776, when the thirteen American colonies declared their independence from the British Empire. This day is celebrated as Independence Day in the United States every year. The history of the country can be divided into various periods, such as the colonial period, the Revolutionary War, the formation of the federal government, westward expansion, the Civil War, the industrial revolution, the world wars, and the civil rights movement, all leading up to the present day.