Frequently Asked Questions


1. When did the mill open?

The exact date that the mill opened is unknown. Construction of the mill started in 1820 with work also done to the structure in 1829.


2. How does the mill run — where’s the motor?

There s no electric motor. The mill operates totally by water turning the waterwheel.

3. How much of this building is original?

The exterior walls, main support beams, floor joists, most of the flooring. (some of which was replaced in the 1930s), and the roof rafters.
4. Where does the water come from?

When the mill was last used, the water came from a 2—inch city water pipe. When the mill was grinding, the water was pumped from this same pipe, as well as from a recirculating pump located under the water wheel. The pump increased the amount of water going down the raceway so that the speed of the stones was fast enough to grind the flour or meal. We are still discussing where the water will come from after the mill is restored. Most likely it will be pumped from the creek.
5. How do the inside gears move?

A. The gears inside are moved by the water wheel outside of the mill. The water wheel is turned only by the water; there are no hidden electrical motors.

6. Why is wood used for the gears?

A. Originally wood was used because metal was scarce and expensive. Wood has continued to be used because if a wooden tooth broke, it could be more easily repaired/replaced. Wooden gear teeth and cogs were commercially produced into the 1950s and 60s.

7. How long do wooden water wheels last?

Most wooden waterwheels can be expected to last between 20—30 years. Rot causes them to be replaced.
8. What are the belts made of?

The belts are made of leather, before leather belt drive was used, rope drive was common.
9. Where does the grinding occur?

The grinding takes place on the first floor of the mill under the round wooden covers, which contain the millstones.

10. Where was the original dam?

A. From old maps of DC the seems to have been upstream near Broad Branch.


11. Where was the mill race?

There are three races in the mill’s history. The first race was used from the 1820s to the 1870s. Up until 1914, the Luffel turbine had its own race. With the restoration in the 1930s, the new race came from the stone wall of the dam in a direct line to the wooden cover for the sand trap, continuing to the sluice box, then making a right angle to the water wheel.

12. How often do you have to sharpen the millstones?

How frequently the stones must be sharpened depends on how much you grind. Stones can be dressed anywhere from every few weeks to only once a year.
13. Do the millstones really GRIND the grain into flour?

The flour is not mashed between the stones. The feather edge of the millstone furrows pass each other and shear the grain like the cutting action of a pair of scissors.
14. How does the flour and meal get downstairs?

The angle of the furrows in the millstones and centrifugal force created by the turning of the runner stone move the flour out of the millstones. As the grain moves between the millstone, air is also moving to keep the millstones cool. There is a down draft created from the millstone eye through the millstones down the basement chute, which carries the flour down to the sifter.
15. How do you get flour (white, whole wheat) for example, instead of bran or cereal?

This is done by sifting or bolting the ground material over different size mesh screens or bolting silk. The white flour, being the finest particle size, is sifted through the finest mesh, the cereal the next largest, and bran being the largest will be sifted out last in the largest screen.
16. What do you do with the leftovers from the sifting?

The leftovers, being bran and the middlings, are used for animal feed. In the early days of milling in this country, there was no feed business. Then, millers discarded the leftovers by dumping them into the creek.
17. Was flour always sold in bags?

Flour was first sold in paper bags in the 1930s. Before that it had been sold in cloth bags (100 lbs.). Originally flour was sold in wooden barrels, holding 196 pounds.
18. Where does the flour go after it is ground?

The flour comes from the millstones down a chute to the basement of the mill. There it is either placed over a meal box sifter or into an elevator, for sifting and packaging elsewhere.
19. Why should you keep flour and meal in a cool, dry place?

Stone—ground flour and meal contain parts or most of whole grains and no preservatives. The germ is naturally oily and will cause the flour to turn rancid. The bran is a light, airy material which will absorb moisture easily, thus reducing the keeping quality in the flour and meal. A cool, dry place, such as a refrigerator or freezer, will add to the shelf life.
20. Are there many fires in mills?

Actually, few mills suffer from fire as compared to other structures and industries. There is no friction in the milling process that would cause fire. A fire may be started if the millstones hit, generating sparks which could ignite the flour dust. Or a cloth or leather belt binding up, with a drive pulley underneath it continuing to turn, could cause heat and friction to build up, but usually this is unlikely, especially if the mill is operating correctly.

21. Do particles of the millstones end up in the flour?

No, the millstones do not touch in grinding, so no particles end up in the flour. If the millstones are not purged enough after dressing, stone particles from the millstone dressing will end up in the flour.

22. Why does the mill have Dutch doors?

These doors keep out stray dogs, and young children from entering the mill, but still allow the breeze to flow through.

23. Which shaft broke in 1897?

It is not known what shaft or part of a shaft broke, but it was removed in the 1930s. From the 1870s to 1897, the mill operated with a James Leffel Turbine. The main shaft is a 4 7/8—inch steel shaft, which would never break. The problem with the Leffel turbine was a series of gates around the circumference of the turbine, which were opened or closed through linkages operated from above. This arrangement allowed a mill operator to shut off one or more turbines without having to shut down the entire water supply to other wheels (turbines) operating at the same flume. The gate control arms are very prone to breakage


24. What was used as grease when the mill operated?

The millers use the same product they use today animal suet.

25. What else was located here with the mill?

At Pierce Mill there was also a still house where grain products were stored that weren’t sold as flour and meal. Mr. Pierce also had a saw mill, which was common to have with a grist mill. He also had several barns and outbuildings, a distillery, and a spring house. Near some mills there was also a general store, and a post office.
26. How many millers are there today?

It is hard to say, since no one keeps track. The Society for the Preservation of Old Mills does publish lists of different states, but they are not complete.
27. What is the correct way to spell the name of the mill?

The spelling of the name Peirce/Pierce has been a controversy for quite some time. The name is spelled “ei” on Isaac Peirce‘s will and on their family vault in Rock Creek Cemetery. Other sources say it was changed when Isaac Peirce’s grandson’s name was “Pierce Shoemaker”.

28. Where’s the bathroom?

There are facilities located behind the barn.

29. Where’s the nearest pay phone?

Across the street (Tilden), next to the picnic pavilion.
30. Where’s the nearest metro stop?

The nearest stop is Van Ness University of the District of Columbia on the Red Line at Connecticut Avenue.

Did You Know?