Less than a month after its opening, a $69 million exhibit beneath the Lincoln Memorial is plagued with problems, potentially endangering rare American artifacts, according to three National Park Service officials and internal communications reviewed by City Cast DC.

It’s the latest in a string of troubles involving upgrades around the National Mall unveiled as part of America’s 250th birthday celebrations. In this case, the Lincoln Memorial Undercroft opened to the public on June 25 and displays rare copies of the Emancipation Proclamation and the 13th Amendment to the Constitution, both bearing the original signature of President Abraham Lincoln. The documents – treasured turning points in the nation’s effort to end slavery – date back to the 1860s and are worth millions.

But three National Park Service employees, who spoke on the condition of anonymity because they were not authorized to speak publicly, described a facility with faulty security measures. Notably, the employees said, the Park Service has struggled to maintain proper conditions for its rare and delicate documents. Screens designed to shield the records from harsh light have been defective and temperatures inside the display case have repeatedly reached more than 80 degrees, according to the Park Service officials. Experts say that’s a violation of professional standards for housing historic documents and hot enough to accelerate decay.

A Park Service spokesperson said Monday that staff actively monitor the environmental conditions of the exhibit and “continually manage the space to ensure the documents are cared for.” The spokesperson did not answer questions about the temperature in the documents’ display case – including its temperature Monday night, the hottest temperature the case has reached since the museum’s opening, and the target temperature for the documents.

Last Friday, City Cast DC observed a fan pointed toward the display case. The Park Service did not respond to questions about why the fan was there.

Katie Lowe, a preservation specialist with the Conservation Center for Art and Historic Artifacts, said historic documents should never be exposed to temperatures above 75 degrees — and even then, she said, that level of heat is only safe if humidity and light are carefully controlled. The list of risks from high heat is long, Lowe said: mold, embrittlement, yellowing, ink corrosion, pests and more.

“Decay is a chemical process and when you introduce heat you accelerate chemical processes,” Lowe said.

The National Archives stores the Charters of Freedom — a display that includes the Constitution and the Emancipation Proclamation — at 67 degrees inside state-of-the-art cases that monitor internal pressure, temperature, relative humidity and atmospheric conditions. The National Archives website urges the public to store family archives below 75 degrees to “slow the rate of chemical decay and reduce insect activity.” The Northeast Document Conservation Center says the best practice is to store important documents between 64 and 72 degrees.

Inside the Lincoln Memorial Undercroft. (National Park Service/Kelsey Gracyzk)

The documents at the Undercroft exhibit are on loan from hedge fund billionaire and philanthropist Kenneth C. Griffin through June 2027, the National Park Foundation told the Washington Post. Griffin, who purchased the documents at an auction last year for a reported $18 million, did not respond to requests for comment.

Lowe said she was mystified by why the exhibit was displaying the original copies instead of facsimiles — exact copies that are often indistinguishable from the original to the naked eye and commonly used in museums to protect fragile artifacts.

“A year is certainly enough time for damage to occur,” she said.

In a statement, the Park Service spokesperson said: “These documents are being cared for as agreed with the donor and the National Park Foundation, and the National Park Service remains in regular communication with all parties regarding their stewardship.”

The copy of the Emancipation Proclamation is one of 27 known remaining copies printed for a Philadelphia fundraising fair in 1864. The proclamation declared that all enslaved people in Confederate states were free (though it did not end slavery altogether) and allowed the enlistment of Black soldiers. Lincoln signed 48 copies of the document to raise money for hospitals, wounded Union soldiers and families who had lost loved ones in the war.

The copy of the 13th Amendment on loan to the memorial is also rare, one of only 15 known copies like it. In addition to Lincoln, it’s signed by 37 senators and 114 members of the House.

The documents are not the only concern among Park Service employees. Two officials said that the museum’s “sally port” entrance system — a security measure involving two sets of doors that cannot be unlocked at the same time — is broken. City Cast DC confirmed this last week after seeing a young child push open the first set of doors while the second remained ajar. Plus, employees say there have been other issues, including a power outage on Saturday that shut the museum down for the day and a glass door that shattered on a visitor in the elevator bay. (No one was harmed.)

A Park Service spokesperson confirmed the Undercroft uses a sally port entrance system “to safeguard visitors and the Lincoln Memorial” but did not respond to the claims that it was faulty. The spokesperson confirmed that a contractor is working to repair a “malfunctioning door” after a collision with an electric wheelchair, but said it does not affect the security of visitors or the exhibit.

From the Great American State Fair power outages to the Reflecting Pool algae bloom, from artists dropping out of concerts to the weather delaying the Fourth of July fireworks, America’s 250th anniversary celebrations in D.C. have not always gone according to plan.

However, unlike some other events, plans for the Lincoln Memorial Undercroft have been underway for a decade. The exhibit was announced in 2016, the same year Congress established America250 as a nonprofit led by a bipartisan group of lawmakers and citizens. This is different from President Donald Trump’s Freedom 250, a public-private partnership he established shortly after his second term began that has been behind many high-profile celebrations, including the fair and fireworks show.