The 4th of July is the national holiday in the USA. It celebrates the Declaration of Independence (written by Thomas Jefferson…) which was adopted on July 4th, 1776. At that moment, the American colonies declared independence from Britain.
A video on Independence Day =
http://www.history.com/topics/july-4th/videos#fourth-of-july-history
Some information in French : http://french.france.usembassy.gov/a-z-independance.html
