Chapman's Mill, built in 1742 the ground grain was shipped to Alexandria and then to South America and Europe. In 1876 the Beverley family restored the mill and operated it until 1951. More details on the Mill.
Photos from my hike of the Bull Run Mountain Conservancy Trail in Virginia, April 2004. I believe I found this hike in 60 Hikes within 60 miles of Washington DC, which is a great book. More photos and detailed map, etc.. More information on Chapman's mill (or Beverley Mill)