Beverley Mill, also known as Chapman Mill, is a historic grist mill located north of Interstate 66 and Virginia State Route 55 in Thoroughfare Gap near Broad Run, Virginia, straddling the county line between Prince William and Fauquier Counties. It was built about 1759, and is a five-story, four bay by three bay, rubble stone structure. The water power was p…Beverley Mill, also known as Chapman Mill, is a historic grist mill located north of Interstate 66 and Virginia State Route 55 in Thoroughfare Gap near Broad Run, Virginia, straddling the county line between Prince William and Fauquier Counties. It was built about 1759, and is a five-story, four bay by three bay, rubble stone structure. The water power was provided by Broad Run which, in its 1,300-foot passage through the Gap, drops 87 feet. Exterior mill machinery included a 29-foot metal waterwheel and sluice gate as well as a stone mill race. The mill continued in operation through World War II. It is included in the Thoroughfare Gap Battlefield.