Sept. 17, 1862, was the bloodiest battle day in United States history. More Americans — some 3,600 — died as Northern and Southern armies clashed at the Battle of Antietam, in western Maryland, than on any other single day before or since, even more than on Sept. 11.

One hundred and fifty years later, as the National Park Service commemorated the terrible loss at Antietam, I stood on the stage in a large tent on the battlefield before several hundred eager tourists, curious locals and enthusiastic Civil War buffs of every age and origin.

We had gathered to discuss a documentary made by Ric Burns based on a book I had written about death and the Civil War, a chronicle of the experiences of more than 700,000 Americans who died between 1861 and 1865, leaving a nation of mourners in a world profoundly altered by the scale of such human tragedy. The audience posed questions to Ric and me about history, about war, about patriotic sacrifice, about American identity, about the meanings of life and death and human mortality — and about how all those things were both different and the same across the century and a half that separated us from our Civil War ancestors.

Ric’s film, and the moving discussion it generated, were made possible by the National Endowment for the Humanities. Reports suggest that the Trump administration’s coming budget will defund the endowment.

I would wager that few readers of this newspaper, and probably few Americans anywhere, are untouched by an N.E.H.-sponsored project or program. In 1990, for example, Ric Burns and his brother Ken produced an 11-and-a-half-hour documentary on the Civil War that was broadcast over five consecutive nights and seen by more than 40 million viewers. For much of the nation, it was an early form of binge-watching. The humanities endowment made that film possible. ...