If you really want to learn about the 4th of July, I would recommend “Fun Facts for July 4” at the Washington Post website.
http://www.washingtonpost.com/news/morning-mix/wp/2014/07/03/fun-facts-for-july-4/
For example, three of the first five U.S. presidents died on July 4. John Adams and Thomas Jefferson died in 1826, the 50th anniversary of the country’s birth. (Adams’ last words were recorded as “Thomas Jefferson still survives”, but that can’t be proven and he had no way of knowing that Jefferson had already died a few hours earlier). James Monroe, the fifth president, died five years later in 1831.
The date itself was a bit arbitrary. The Continental Congress met on July 2nd and voted to approve the resolution for independence. After a draft by Thomas Jefferson and editing by John Adams and Benjamin Franklin, the Declaration of Independence was presented to the Congress two days later and adopted then, but it wasn’t signed by most of the delegates until Aug. 2.
But of course, none of that is important now.