ASME-Landmark:Colvin Run Mill

Colvin Run Mill is an early 19th century operating gristmill, closely modeled on the principles developed by Oliver Evans (1755-1819). Powered by a waterwheel, the restored mill was probably built on or after 1811 on the site of an older mill. Originally, the site was the property of George Washington, who identified it as ideal for a mill site.

The design of the Colvin Run mill allows the owner to load, convey, sift, grind, separate and dry grain into various desired grades with very little manual labor. Each of the four floors of the building served a specific function in turning the grain into flour or cornmeal. Visitors can see an Evans-designed hopper boy (mechanized raker), a grain elevator, wooden Archimedean screws to push the grain through the chute, a bolting chest and shaker assembly (for sifting), and a beam scale for pricing. According to the Society for the Preservation of Old Mills, this mill contains what may be the only operating hopper boy in the United States.

Water from Difficult Run is diverted into the millrace to power the 20-foot overshot waterwheel. The waterwheel produces up to 26 horsepower, turning (outside) at a rate of 10 rpm, resulting in a top grind stone rate of 100 rpm. The gears and machinery are made almost entirely of wood, dating them prior to 1850 before metal fittings commonly replaced wooden ones.

Changing hands several times, the mill operated commercially until mid-1930s. It was abandoned until 1965, when the Fairfax County Park Authority acquired the property, restored it to the Evans design, and reopened it as a historical site in 1972. See ASME website for more information