The 150-year-old, recently digitized map depicts the Battle of Antietam — not with the usual scenes of charge and counter-charge, but as one vast cemetery.

And Civil War historians are hailing it as an important new way to visualize the toll of the huge battle outside Sharpsburg, Md., in 1862.

“Every one of us who’s looked at this absolutely flips out,” said Garry Adelman, chief historian for the Washington-based American Battlefield Trust, which works to preserve historic battlefields. “This will reverberate for decades.”

The map is the only one of its kind known to exist. It was digitized by the New York Public Library, which owns it, and was spotted online by local historians a few weeks ago.

It depicts the locations of 5,800 graves spread across a landscape of about 12 square miles.

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Although most of the Antietam dead were moved to formal cemeteries after the war, the map was drawn up before that happened, Adelman said, perhaps in conjunction with the planned relocations.

And the grave clusters are grim new indicators of where the fighting was worst.

“It’s a visual representation of the carnage from the battle,” said Timothy H. Smith, the researcher who first stumbled on the map online. “It’s startling to look at.”

The map provides the names in some cases of the regiments or brigades to which the dead belonged. And in about 45 cases it provides the names of individual buried soldiers.