A limekiln is a hollow masonry structure used to burn limestone (calcium carbonate) to create lime (calcium oxide). It was round or square in footprint, built into a bank, and tapered from bottom to top. An opening in the bottom accommodated a flue. Inside the kiln, firewood was laid, topped with layers of coal and limestone. Once burning commenced, it took several days to reduce the stone to lime. Lime was used on farm fields, in masonry, for plaster, for whitewash, and as disinfectant.

Clinton County Limekiln
Limekiln, Clinton County, early twentieth century.
(Image from the Historic American Buildings Survey, Library of Congress,
Prints and Photograph Division, Digital ID hhh.pa3678)