Incorporating the most advanced technological improvements of the era, Aldie Mill was designed to accommodate the labor-saving machinery of Oliver Evans. In the early 1800s, Evans revolutionized the processes of flour manufacture by devising a mechanical system that performed every necessary movement of grain and meal from one part of the mill to another without the aid of manual labor. While other prominent Virginia mill owners, most notably George Washington and Thomas Jefferson, employed Evans’s revolutionary system in their mills, Mercer's use of this machinery at Aldie is particularly well documented. Among Mercer's surviving business correspondence for 1809 is an application for a license to use Evan's patented inventions, a purchase order for Evan's cast-iron machine for breaking plaster into fertilizer, and the young miller's request on behalf of his millwright for Evan's technical assistance in fitting the plaster machine to his mill.

Although the Evan's machinery and the early wooden water wheels were replaced at the beginning of the 20th century by the present Fitz metal water wheels  and machinery, Aldie Mill nevertheless preserves much of the original character of the old Evans system. Much of the early machinery remains intact, including imported burrstones from French quarries in La Ferte sous Jouarre.   Wooden portions of the mill include hand-hewn chamfered beams and chestnut door frames. The mill complex remains much as it was in Mercer's time.