Wood charcoal fueled the forges in the nailery on Mulberry Row and heated the stoves in the kitchen. Charcoal was stored under lock and key in wooden sheds that once stood here. Built about 1794, these "coal sheds" likely resembled temporary lean-tos and functioned as secure holding areas for fuel that could be easily transported to the nailery, smith's shop, or the main house. Additional sheds, each holding 8,000 bushels of charcoal, may have been built as fuel needs increased on Mulberry Row. The nail-making operation, for example, demanded large amounts of fuel; Jefferson calculated that, on average, 666 bushels of charcoal would be needed to make 172,480 nails in the nailery.
In the spring of 1800, Frank, an enslaved charcoal-burner, produced most of the charcoal in "coal-kilns" on the mountaintop; he learned his trade from the German charcoal-burner Jacob Silknitter. David Hern, Lewis, and six hired slaves cut 200 cords of "coal wood" for Frank to use for charcoal production. Charcoal-burners like Frank earned a "half dime for every bushel to the cord of wood" that their kilns yielded. Jefferson used cash incentives to maximize the efficiency of work performed by Frank and other enslaved charcoal burners—James Hubbard, Cary, and David Hern. (Marker Number 11.)