The history of the United States goes back thousands of years, when people migrated across the Bering Strait into North America. The discovery and the colonization of America by European powers shook up the continent and new ideas, people and culture flew in. By 1775, present-day United States was split into roughly three thirds: the eastern part belonged to Great Britain; the central part belonged to Spain; and the western part belonged to Spain as well. In 1776 colonists in the British colonies rose up, and by 1783 had asserted their independence. With an independent Canada to the north, the history of the United States changed.