July 4th, 1776 -- the United States of America declared independence on this day.

AmericanCulturalAssumption''''s:
 "Independence Day"
 http://directory.google.com/Top/Society/Holidays/Fourth_of_July/

Technical note:  The final document was actually adopted by the Second Continental Congress on July 2, and published on the 4th.
But perhaps only the president, John Hancock, and the secretary, Charles Thomson, signed that day.  The final signature, Thomas M''''''cKean, was not affixed until several years later.
-- http://www.mi.lp.org/op-ed/oped0701.htm

"The second day of July, 1776 will be the most memorable epocha in the history of America."
-- John Adams

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AmericanCulturalAssumption:  "Independence Day"

''Indeed, as in this wonderful quote from news.com. "some tech workers in other countries will not use Independence Day as an excuse to liberate themselves from their desks. ". Really, how inconsiderate. Perhaps it's because it's not their Independence Day? http://news.com.com/2100-1017-940653.html''

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The Declaration of Independence:
http://www.law.indiana.edu/uslawdocs/declaration.html

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Other information about this date:

"Nothing of importance happened today". -- King George III's private diary (king of England at the time)

"Good riddance day." -- some of my English friends.  ;->

trivia:  http://www.envirobx.com/Bryan_henry_fourthofjuly.htm