Maryland Sens. Chris Van Hollen and Angela Alsobrooks called on the federal government to halt efforts to “whitewash American history” at Harpers Ferry National Historic Park in West Virginia, they said in a joint letter on Tuesday.

The senators’ letter was sent to the U.S. Department of the Interior two weeks after The Washington Post reported the Trump administration ordered the removal of signs at monuments and sites that were related to slavery. The Post reported that Harpers Ferry National Historic Park, where John Brown led a rebellion to free enslaved people, is one of the targets in the administration’s latest directive.

In their letter, Van Hollen and Alsobrooks said they were concerned about reports of more than 30 signs at Harpers Ferry being ordered to be removed or covered. Those signs reportedly referred to racial discrimination and detailed the hostility toward formerly enslaved people in Harpers Ferry, according to their letter.

The National Park Service did not confirm that there was an order to alter the signage at Harpers Ferry, but said in an email that actions at the national historic park were ongoing.

The potential changes at Harpers Ferry are part of a larger transformation of national historical sites and monuments under President Donald Trump’s “Restoring Truth and Sanity to American History” executive order signed in March.

The executive order directed agencies to review and change information shown at historical museums, parks and monuments to remove what the order calls “corrosive ideology” and replace it with positive messaging about the United States.

This has resulted in changes to American cultural institutions and websites dedicated to them. A web page dedicated to Harriet Tubman on the NPS Underground Railroad website, temporarily removed the words “African American,” “bondage,” “enslavement,” “self-emancipation” and “escape.” The change was reversed after public outcry.

Some historians and researchers worry that other institutions in Maryland could see their history deleted, including the former plantation that has become the Hampton National Historic Site in Baltimore County.

Paul Shackel, a professor in the Department of Anthropology at the University of Maryland, spent nearly eight years working for the National Park Service at Harpers Ferry before joining UMD in 1996.

He said the job of a NPS employee and an academic is “to tell all of America’s story.”

“These difficult histories are important for us to learn, so we can move forward,” Shackel said.

The main historical center of Harpers Ferry National Historic Park is in West Virginia, but parts of it extend into Maryland and Virginia. The Potomac and Shenandoah Rivers flow through its historical and hiking lands.

Several significant events in American history, especially during the Civil War era, took place at Harpers Ferry. It’s the location where John Brown, a white abolitionist, recruited a group to raid the National Armory and Arsenal in an attempt to overthrow government leaders and free the enslaved people there.

After the two met in Canada, Harriet Tubman was documented helping John Brown plan the raid. Shortly after the raid failed, the Civil War began, and Harpers Ferry became a battlefield.

The site is also home to Storer College, one of the first places in the country where formerly enslaved people could receive an education.

Shackel said it’s frightening that the administration has the power to change American history.

“It’s about the industrial revolution, it’s about John Brown, it’s about slavery, it’s about emancipation,” said Shackel. “I think we need to work hard as a community to keep these stories alive.”