When Ben and Riley are talking on the steps in front of the Lincoln Memorial, the water in the reflecting pool was digitally added later. The pool had been drained for maintenance at the time of filming.
The movie includes footage from the first filming allowed in the tower of Philadelphia's Independence Hall.
The movie suggests that something is written on the back of the Declaration of Independence. It is true that something is written on its back. 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 29 3/4 inches by 24 ½ inches) was rolled up for storage. So, it is likely that the notation was added simply as a label.
Ben, Patrick, and John Gates were all named after founding fathers (Benjamin Franklin, Patrick Henry, and John Adams). Abigail Chase is a combination of Abigail Adams, wife of John, and Samuel Chase, a signer of the Declaration of Independence and later an Associate Justice of the United States Supreme Court.