Factual error: In the scene under Trinity Church, Ben is holding on to the elevator and trying to get a grip to swing to safety (after Dr. Chase is already to safety). He grabs a board that falls off, then the last board pulls back an is shown to be held on with modern day nails. If it were built 200 years before, as the movie suggests, these would not likely be the kind of nails from the local hardware store as shown in the film.
Character mistake: At the gala, Ben describes to Abigail how the Founding Fathers would have been hanged, beheaded, drawn and quartered, and had their entrails burned had they lost the war. However, only hanging and beheading were acceptable practices in Britain at the time; Ben's information is off by several decades.
Continuity mistake: When Ben is in the Men's restroom taking off the overalls to reveal his tuxedo, he is in front of the third or back sink. He turns, throws tool belt away, turns back toward mirror and grabs his drill and starts to leave with the red NO SMOKING sign on the mirror up to his left. Then he stops to look in the mirror again as Riley says "How do you look?" He is looking into the mirror straightening his tie and the red NO SMOKING sign is on his right. The next frames he is back in front of the third sink smoothing his hair back and the NO SMOKING sign on his left.
Continuity mistake: The Declaration of Independence in the clear plastic cover keeps changing colors from brown to white and back. When Ben puts it in the very first time while in the elevator, it is brown. When Ian gets the case out of the street after Abigail loses it, it is white. It is back to brown in the church.
Factual error: When Riley is sitting outside the Franklin Institute and sees the ad on the side of the bus with the close up of the Liberty Bell, the SEPTA bus is labeled with the 108 Airport route. That bus route goes from the 69th Street Transportation Center to the Philadelphia International Airport and would not pass near the Franklin Institute.
Continuity mistake: When Sadusky has Ben handcuffed across the desk from him, there is nothing on the desk directly between Sadusky and Ben except Sadusky's coffee mug, a gray thing that is about mid-way between Ben and Sadusky, and a white spiral notebook to the right of the coffee mug. Then Ben says, "Ian still ended up with the Declaration of Independence," and as the shot switches from Ben to Sadusky saying, "Because of you," we see the glasses Ben found at Independence Hall appear on the desk in front of Sadusky between the gray thing and himself. Then as Sadusky says, "Someone's got to go to prison, Ben," and Ben says, "Yeah," two short stacks of papers appear on the desk in front of Sadusky and the glasses changes position as well.
Continuity mistake: This concerns National Treasure 1 and 2. In the first film, when Ben's grandfather tells Ben the story about the clue given to Thomas Gates, he says he was the grandfather's grandfather's, grandfather - Ben's Great, great, great, great grandfather. In the film, in 1832, he appears very young, maybe early 20s. But in the second film Thomas Gates, Ben's Great, great grandfather, appears to be 40-50 in 1865. A young man in 1832 can't have a middle aged grandson in 1865.
Character mistake: When Ben, Riley, and Abigail are in Independence Hall in Philadelphia and roll out the Declaration of Independence to inspect with Ben Franklin's special "ocular device" that Ben had just found, Ben pauses to take in the moment. When asked what was the matter, Ben says "It's just that...the last time this was here (in Independence Hall)...It was being signed." However, according to archives.gov, "In 1876 the Declaration traveled to Philadelphia, where it was on exhibit for the Centennial National Exposition from May to October. Philadelphia's Mayor William S. Stokley was entrusted by President Ulysses S. Grant with temporary custody of the Declaration. The Public Ledger for May 8, 1876, noted that it was in Independence Hall "framed and glazed for protection, and... Deposited in a fireproof safe especially designed for both preservation and convenient display." Sorry Ben.
Other mistake: The signature on the copy of the Silence Dogood letter is different than the one on the original. They should be the same if it was truly a scan.
Continuity mistake: When Ben is trying to pay cash for the 'replica' of the Declaration of Independence in the Gift Shop, he lays his wallet down on the counter and starts counting out bills and change right next to his wallet on the counter. A few scenes later, when the FBI is reviewing surveillance tapes, one of the monitors shows Ben reaching in his pocket, pulling out his wallet and grabbing the money that is out on the counter. This happens when the over voice says, "Charge. Benjamin Gates."
Other mistake: When Ben enters the Gala dressed in overalls and tool belt, he enters a door across the street from where Riley is parked. There is a security guard outside that door who waves Ben on into the building. As Ben exits that same door, there is no security guard, which seems hard to believe with such a big event.
Deliberate mistake: In the two scenes when Ben and Riley are in the documents room, it is in full light. The rotunda is actually dimly lit as a way of protecting the documents from light damage.
Visible crew/equipment: Three times you can see lens flare as the camera is pointing towards the sun: the airborne-shot of the Jefferson Memorial (in this one you can even see a part of the airplane or something else in the lower left corner), the Philadelphia skyline as they drive into Philadelphia, and the view from the "target location" of the shadow of the cross (near the brick containing the glasses) towards the steeple with the bell.
Plot hole: The tunnel at the base of the stairs under the church wasn't connected to the stairs and seems to only have been reachable with the elevator system.
Continuity mistake: When Riley is in the subway to get the video footage, he starts to record the preservation room that shows the declaration on the desk, but how can It be there if Riley hasn't used the laser to get it moved there yet?
Factual error: The poem on the pipe stem reads Fifty Five in Iron Pen, and Nicolas Cage states "a document that fifty five men signed." The Declaration of Independence was signed by fifty six men.
Deliberate mistake: When Riley uses the video camera laser to disable the Declaration of Independence sensor, that could never happen since cameras are not permitted in the documents room.
Continuity mistake: When Ben and Ian get into an argument over stealing the Declaration of Independence, Ian says "all you're going to be is a hinderance." Shaw then points a flashlight and a gun at Ben. When the camera angle is on Ben, there is no flashlight beam visible on him. Then Ian says, "I'll shoot your friend", Shaw points the flashlight and gun at Riley, the light beam visible on his face. Ben lights a flare. Shaw points the flashlight and gun back on Ben, and again, no flashlight beam is visible on him.
Continuity mistake: After everyone gets off the elevator down under the church, Ben has the declaration of independence then Riley has it without Ben giving it to him.
Continuity mistake: In the scene where the group are revealing the cipher on the back of the Declaration of Independence, in a wide shot, we can see glass on the corners of the Declaration to keep it in place. When Abigail rubs the Q tip on the right corner, the glass is gone.
Answer: "The Secret Lies With Charlotte" ~ Charles Carrol of "Charleston".