STERLING, Va. — When Donald J. Trump bought a fixer-upper golf club on Lowes Island here for $13 million in 2009, he poured millions more into reconfiguring its two courses. He angered conservationists by chopping down more than 400 trees to open up views of the Potomac River. And he shocked no one by renaming the club after himself.

But that wasn’t enough. Mr. Trump also upgraded its place in history.

Between the 14th hole and the 15th tee of one of the club’s two courses, Mr. Trump installed a flagpole on a stone pedestal overlooking the Potomac, to which he affixed a plaque purportedly designating “The River of Blood.”

“Many great American soldiers, both of the North and South, died at this spot,” the inscription reads. “The casualties were so great that the water would turn red and thus became known as ‘The River of Blood.’ ”