Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Preserving Our Nation’s Watchwords: The Charters of Freedom Encasements

We all know the words:

“We hold these truths to be self-evident, that all men are created equal …”

“We the people of the United States, in order to form a more perfect Union …”

“Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press …”

Bold statements written by visionaries giving birth to a new nation. These are the opening lines of the Declaration of Independence, the Constitution of the United States and the Bill of Rights—the three documents known collectively as the Charters of Freedom—that have preserved the rights of Americans for more than 200 years. The task of preserving these hallowed pages of parchment has been entrusted twice to the National Institute of Standards and Technology (NIST). 

A man looking at the Declaration of Independence in its NIST-designed and manufactured encasement
A visitor to the National Archives in Washington, D.C., views the Declaration of Independence safe within its NIST-designed and manufactured encasement.
Credit: National Archives and Records Administration

It all started in 1940 when the Library of Congress commissioned NIST’s predecessor, the National Bureau of Standards (NBS), to design and manufacture “sealed receptacles” that would protect two of its most prized possessions, the Declaration and the Constitution, from degradation while providing the public with an unobstructed view. The project, delayed by World War II, was finally realized in 1951 when NBS engineers permanently sealed (or so they thought at the time) three documents—the Bill of Rights had been added in the interim—inside state-of-the-art glass and metal encasements and delivered them to the Charters’ new home, the National Archives and Records Administration (NARA) in Washington, D.C. The cases were technological marvels, keeping their treasured contents free from the ravages of temperature, light and humidity, as well as their most destructive enemy, oxygen (the chambers were filled with helium, an inert gas). Innovations included electronic leak detectors built into the frame, laminated glass that absorbed harmful ultraviolet light and a pure cellulose backing that removed any moisture.

A NIST scientist stands before the Declaration of Independence, which is upright in glass, and works on the encasement
Chemist E. Carroll Creitz of the National Bureau of Standards (predecessor to NIST) works on the 1951 encasement for the Declaration of Independence that protected the document until 2003 when an improved preservation system replaced it.
Credit: NIST

In 1995, Archives preservationists, with the help of NASA technology, examined the encasements and detected microscopic fissures in the glass plates that held the document pages upright for viewing. They feared that the cracks would eventually let in pollutants. Additionally, constant contact between the parchment and the glass threatened to lift the ink off the pages. Correcting these problems was practically impossible because the cases had been soldered shut and could not be opened without compromising the protective helium atmosphere.

So, in a case of historical déjà vu, the Archives turned again to NIST for a scientific solution. A team of scientists, engineers and technicians from NIST, NARA, NASA and private company Heery International spent the next four years designing, fabricating and testing a set of remarkable replacements for the outdated 1951 preservation system.

A side view of the DOI encasements with a NIST engineer working on them.
NIST engineer Chris Evans works on the agency’s “second” home for the Declaration of Independence in 2002.
Credit: NIST

Among the features in each encasement: an aluminum base and titanium frame both machined from single pieces of metal to eliminate potentially leaky seams; an atmosphere of argon gas, with larger molecules than previously used helium, to minimize leakage; laminated, tempered glass that does not touch the parchment; built-in window ports, sensors and instrument bays for monitoring the internal environment; the flexibility to position a document for optimal viewing by all visitors; and most importantly, the ability to open the case—if it’s ever necessary—and then easily reseal it.

Top image: Diagram of the NIST-designed and built encasements with the parts (document, glass, seal, frame, base pockets, ball and socket, optics, diagnostic windows, base and platform) labeled. Bottom image: Model of one part of the encasement.
Cutaway diagram and model showing the components of the current NIST encasements for the Charters of Freedom documents.
Credit: NIST

Since the completion of the Charters of Freedom Re-encasement Project in 2003, more than a million persons annually have visited the Rotunda of the National Archives to see “America’s Founding Documents” safe in their NIST-built homes. 

Did You Know...?

The NIST encasement had a co-starring role in the 2004 movie “National Treasure” when treasure hunter Benjamin Gates (Nicolas Cage) carries the still-encased Declaration of Independence out of the National Archives Preservation Room to save it from thieves. While the scene is thrilling, it does bend the facts in three ways:

  • The encasement is designed to be easily lifted by two people; one person, as seen in the film, cannot do it alone.
  • The encasement is rigidly sealed by 66 steel bolts, making it impossible for anyone to remove all of them in the short elevator ride depicted in “National Treasure.”
  • The glass of the encasement is a two-layer, 0.95-centimeter (0.38-inch) thick, heat-tempered sheet capable of withstanding variations in barometric pressure and temperature, but not bullets. In the film, Gates protects himself from gunfire by holding the encasement in front of him.

– Michael E. Newman

Created June 20, 2017, Updated March 28, 2024