The boy was around 14 when he joined the Continental Army. He signed his enlistment papers with an “X,” suggesting that he’d never learned to write his name. During his three-and-a-half-year military career, he marched more than 1,000 miles. When he died at the Battle of Camden in South Carolina in 1780, he was buried in an unmarked grave and forgotten for nearly 250 years. Researchers excavated the boy’s remains in 2022. Now, they’ve discovered this young soldier’s identity: His name was Private John Pumphrey, and he was one of America’s oldest John Doe cases. “As far as we knew,...