In U.S. history, the Declaration of Independence is a document that was approved by the Continental Congress on July 4, 1776, and that announced the separation of 13 North American British colonies from Great Britain. Accordingly, the day on which the final separation was officially voted was July 2, although the 4th, the day on which the Declaration of Independence was adopted, has always been celebrated in the United States as the great national holiday—the Fourth of July, or Independence Day.

Source: Britannica