The reason we celebrate Independence Day on the 4th is because of the Declaration of Independence, a document that wasn’t so esteemed as now until Lincoln, a document that hung on a wall of the National Gallery exposed to natural sunlight for a very long time, which is why it’s about to disintegrate now. Lincoln called upon the document in the Gettysburg address and elsewhere, recalling the self-evident truths that all people are created equal and have the inalienable rights to life, liberty, and the pursuit of happiness. Seems like a good reason to celebrate to me. Bring on the fireworks!

Links:
Wikipedia
The Declaration of Independence at the National Archive
Thinkin’ Lincoln: a webcomic
More on the Declaration, including influence on Lincoln