It's just so easy to say Happy FOURTH of July, but it's largely unknown that the legal separation of the original 13 colonies in the Americas from Great Britain, was on July the SECOND, 1776.

A resolution of independence by Richard Henry Lee of Virginia was voted and approved by the Second Continental Congress on July 2, 1776. 

After voting for independence, the Congress started to turn out the Declaration that would explain the decision, prepared by a committee of five (Roger Sherman, Benjamin Franklin, Thomas Jefferson, John Adams & Robert Livingston), with Thomas Jefferson as the principle author.  Congress debated and revised the declaration until arriving at it's current form, and approving it on July 4th, 1776.

John Adams wrote to his wife, Abigail:

"The second day of July, 1776, will be the most memorable epoch in the history of America. I am apt to believe that it will be celebrated by succeeding generations as the great anniversary festival. It ought to be commemorated as the day of deliverance, by solemn acts of devotion to God Almighty. It ought to be solemnized with pomp and parade, with shows, games, sports, guns, bells, bonfires, and illuminations, from one end of this continent to the other, from this time forward forever more."

He was off by 2 days.  From the beginning American decided to celebrate on the fourth, the date of the much-publicized Declaration, rather than the date that independence was actually approved in a much less publicized, closed session of Congress.  The myth that the Declaration of Independence was signed on the fourth, was so enduring and established, that even John Adams and Thomas Jefferson (who had each signed the declaration), decades afterward came to believe that they had indeed signed it on the fourth.

So... happy 2nd of July!!