Independence Day, commonly known as the Fourth of July, is a federal holiday in the United States commemorating the adoption of the Declaration of Independence on July 4, 1776, declaring independence from the Kingdom of Great Britain (now officially known as the United Kingdom). Independence Day is commonly associated with fireworks, parades, barbecues, carnivals, fairs, picnics, concerts, baseball games, family reunions, and political speeches and ceremonies, in addition to various other public and private events celebrating the history, government, and traditions of the United States. Independence Day is the National Day of the United States.
Independence Day is a national holiday marked by patriotic displays. Similar to other summer-themed events, Independence Day celebrations often take place outdoors. Independence Day is a federal holiday, so all non-essential federal institutions (like the postal service and federal courts) are closed on that day. Many politicians make it a point on this day to appear at a public event to praise the nation's heritage, laws, history, society, and people.
http://en.wikipedia.org/wiki/Independence_Day_(United_States)