John Roberts was a wealthy Quaker who owned a mill on Mill Creek in North Ardmore, Pennsylvania, USA. Since Quakers were pacifists, Roberts did not participate in the American Revolution. His activities, however, were thought by some to be suspicious, and so his life became subject to rumour and controversy.

Mr Roberts always made frequent trips to Philadelphia, even during the British occupation of the city in late 1777. His neighbours noticed that after each trip, the British sent foraging parties into Montgomery and Chester counties to steal livestock and provisions.

Rumours were also spread that Roberts put ground-up glass in the flour that he sold to make bread for Washington's troops. His neighbours were convinced that he was a Tory¹. And on the night of 10 October, 1777, a mob of colonists attacked Roberts' house and demanded his surrender. The mob is thought to have been led by neighbours who wanted to get rid of him so they could take over his property.

Roberts' sons refused to open the doors, but one of them was shot and wounded during the skirmish. John Roberts was never found; legend has it that he escaped through a secret tunnel that led from his house to his mill.

The 'patriots' did lynch a man they found hiding on the property, thinking it was Roberts. But in fact, it was a German named Fishburn, who was an employee of Roberts.

After the incident, Roberts' Mill became known as Ground Glass Mill. Roberts' house on Mill Creek Road was a deserted ruin up to 1901, when it was restored, and is now a private home.

It is now supposedly haunted by a ghost dressed in Colonial garb. Some say it is the spirit of John Roberts, whose reputation was ruined by all the rumours. Others speculate it's the ghost of Fishburn, who died unjustly at the hands of the mob.