RUTHFULLY YOURS

At first, they might be pleasantly surprised to see the battlefields still intact. But suppose the visiting heroes lean down from their saddles to listen to the park rangers leading tours in green-and-gray uniforms. Expecting to hear a recounting of battles that formed the republic, they instead hear stories about identity politics and climate change. Hamilton, upon returning to his only home, in New York—a site that attracts thousands of visitors annually—would be taken aback to hear, as I did on a visit, park rangers editorialize that he stashed his wife there so he could carry on with his mistress in his Wall Street home.

This casual, official reinterpretation of history has alarmed many modern historians and Americans, including those like me with relatives who served at Valley Forge. In 2016, a park ranger reportedly telling tourists at Independence Hall in Philadelphia that “the Founders knew that when they left this room, what they had written wouldn’t matter very much” resulted in news articles and calls for her resignation. Rangers, however, aren’t required to stick to any script when interpreting the Revolution. Washington and Hamilton might ride on to privately owned Mount Vernon for a more authentic experience.

Traditionally, great powers trust their military forces with protecting and interpreting the sacred battlefields of their founding fathers. After the Revolutionary War, the U.S. military protected the battlefields, conducted “staff rides” to review decisions and scenarios, and encouraged private donors such as the Ladies of Mount Vernon to restore other historical places tied to Washington.

But then came the National Park Service. In the 1920s and early 1930s the NPS was a minor agency struggling for attention and already filled with what today are called environmental activists. These ideologues sought to obtain possession of the nation’s historic sites, which would raise the Park Service’s profile above that of a mere maintenance organization.

In April 1933, President Franklin D. Roosevelt invited Park Service Director Horace Albright for a Sunday drive along Skyline Drive, a new highway the Park Service was building in the mountains of Virginia’s Shenandoah National Park. Albright had already created a “history division” and set up historical monuments. So he took advantage of this time with the president to defeat objections from the War Department, which wanted to keep the battlefields under its purview. Mere months later, by executive order, the War Department transferred 57 historical sites and, more important, the authority to interpret the history of the sites to the Park Service. Albright saw this victory as the culmination of his career.

In the decades since, Park Service historians have been the caretakers of this oral history, codified in a manual written by Freeman Tilden titled “Interpreting Our Heritage.” Tilden plays down military history: “The interpreter in a monument or battlefield of war may thrill his hearer with the account,” he writes, but “these things are an appeal to the mind, to logic and imagination.” Tilden instructs park rangers instead to use “the appeal to the heart,” advocating for a retelling of “the story of how in such tragic environment the human being finds the path to beauty of behavior.”

New Deal workers, through programs like the Civilian Conservation Corps, built replicas of the fortifications, which today’s battlefield visitors may think are real. Washington’s 1775-76 headquarters in Boston was named the Longfellow House to honor the poet Henry Wadsworth Longfellow. It only recently received an amended title, “Washington’s Headquarters,” to reflect the significance of the site where Washington planned how to force the British out of Boston.

That battle, called Dorchester Heights, was also neglected until a lone member of Congress funded the placement of a cannon where Henry Knox secretly rolled 59 of them to intimidate the British to depart. No park ranger is there today. The memorial tower at the Dorchester battlefield is locked, and the area is little more than a spot for dog walking.

The battle of Brooklyn was perhaps Washington’s greatest—20,000 British soldiers surrounded his entire army until the Americans escaped in the fog back to Manhattan. The Park Service offers no tours. The place where Washington crossed the Delaware and led his force of 2,500 in the snow to attack Trenton at dawn isn’t even marked. Meanwhile, enthusiastic, self-funded re-enactors cross the Delaware, as Washington did, on Christmas Day. At least the state governments of New Jersey and Pennsylvania operate low-budget museums on either side.

Congress should probe this travesty. Ranger scripts should be required to include accounts from any one of the dozens of authoritative histories of Washington and the war. President Obama signed a law establishing a commission to plan the celebration of the 250th anniversary of the Revolution, now only six years away. It’s time for Congress to demand a restoration of the interpretation of the nation’s most important historical sites.

Mr. Pillsbury is director of Chinese strategy at the Hudson Institute and chairman of the Battlefields Committee of the Society of the Cincinnati in Washington, D.C.