The movie National Treasure suggests that something is written on the back of the Declaration of Independence. As protectors of this important, original document, we know there is nothing hidden there. But it is true that something is written on its back. See for yourself...
The writing on the back of the Declaration of Independence reads:
Original Declaration of Independence dated 4th July 1776"
and it appears on the bottom of the document, upside down. While no one knows for certain who wrote it, it is known that early in its life, the large parchment document (it measures 29¾ inches by 24½ inches) was rolled up for storage. So, it is likely that the notation was added simply as a label. The writing that appears at the bottom in this view is actually ink from the top of the front side that has seeped through the parchment to the back of the document.