A gristmill is a building with special machinery that grinds grain into flour. For thousands of years, people needed a way to crush wheat, corn, or other grains into the fine powder we use for making bread, and gristmills solved that problem using the power of flowing water or wind.

The word grist means grain that's ready for grinding. Inside a traditional gristmill, water from a stream or river turns a large wooden wheel, which rotates heavy circular stones called millstones. The grain gets poured between these stones, and as they spin against each other, they crush the kernels into flour. The miller who runs the gristmill takes a portion of the flour as payment.

Before factories and modern technology, nearly every town had a gristmill where farmers brought their harvests. You can still visit historic gristmills in places like Colonial Williamsburg, where they demonstrate how this centuries-old process worked. Some gristmills still operate today, grinding grain the traditional way to produce stone-ground flour that bakers prize for its texture and flavor.