The tract of land known as “Black Rock” on Sinclair Creek was patented to John Brisco in September 1760. It was over 50 years before Thomas Hilleary built the eponymous mill, after having purchased a portion of the land known as “Sprained Ankle Tract” from his father, Henry. The Black Rock Mill was built in 1815, and operated as both a sawmill and grist mill. Details are hazy between the mill’s opening and its passage to Franklin Waters and Sarah Hilleary, who sold the mill to Nicholas D. Warfield in…