Aldie Mill was built in 1807-09 and survives today as Virginia's only known grist mill powered by twin waterwheels. For more than 150 years the mill ground for markets along the East Coast and overseas. President James Monroe was an early customer while living at nearby Oak Hill. The mill provided grain for soldiers and their horses during the Civil War. Union Soldiers hid in the wheat bins trying to escape from Confederate partisan John Singleton Mosby. Milling demonstrations when water level permits.