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The Trump administration is enlisting national park visitors into the Republican president’s fight to rewrite American history, with a new directive that forces all park units to display signs that encourage guests to report any information that is critical of American history.

On May 20, U.S. Interior Secretary Doug Burgum directed all park units to display the signs to comply with President Donald Trump’s earlier executive order, which claims that U.S. history has been distorted by ideology and seeks to counter what it describes as revisionist narratives that portray the country’s past in a negative light.

Burgum’s order directs federal agencies and cultural institutions to remove content that “inappropriately disparage[s] Americans past or living,” and to instead highlight the nation’s progress and achievements. It also calls for the removal of what it terms “improper ideology” from museums, monuments and public exhibits under federal control.

In a statement released in March, the American Historical Association, or AHA, condemned the order, defending the importance of historical integrity in public institutions and places. Thirty-six other organizations also signed on to the AHA statement.

“The stories that have shaped our past include not only elements that make us proud but also aspects that make us acutely aware of tragedies in our nation’s history,” they wrote. “No person, no nation, is perfect, and we should all — as individuals and as nations — learn from our imperfections.”

They added, “Patriotic history celebrates our nation’s many great achievements. It also helps us grapple with the less grand and more painful parts of our history.”

All 400 federally managed sites — including those overseen by the Bureau of Land Management, Fish and Wildlife Service, National Park Service, and U.S. Forest Service — will be required to display signs inviting public feedback. The signs will state that the property belongs to the American people and ask visitors to report any areas in need of repair, services requiring improvement, or signage and information that present past or living Americans in a negative light or “fail to emphasize the beauty, grandeur, and abundance of the natural landscape,” according to the National Parks Conservation Association.

Theresa Pierno, the association’s president, said in a Wednesday news release that Burgum’s signs set “a dangerous precedent of prioritizing nostalgia over truth” and would have a “chilling effect” on rangers doing the work of presenting American history at the parks. She said the order could stop rangers from speaking negatively about slavery and the imprisonment of Japanese Americans.

“When the Trump administration tries to rewrite American history, it is the American people who will suffer most,” Pierno added. “... Secretary Burgum should reverse course and rescind this order.”

The sites at risk of being affected encompass some of the most painful chapters in U.S. history. Among them are: Manzanar National Historic Site in California, which documents the incarceration of Japanese Americans during World War II; Sand Creek Massacre National Historic Site in Colorado, where U.S. soldiers killed hundreds of Cheyenne and Arapaho people in 1864; and the Selma to Montgomery National Historic Trail in Alabama, a pivotal landmark where supporters of the Civil Rights Movement marched to call for political reforms. These and other federally managed sites could come under heightened scrutiny as agencies move to implement the directive.

The National Park Service is legally tasked with preserving, protecting and interpreting American history — a mission established by the 1916 Organic Act and reinforced by the 1966 National Historic Preservation Act.