The 1st edition of the historic 25-inch O. S. maps, published in 1876, depicts Llanharry Mill as a working corn mill, but the 2nd edition map (1899) describes it as "in ruins". It was driven by water from the Nant Felin-fach stream, from which a 430 metre-long leat delivered water to a mill dam close to the mill. The 2nd edition map depicts the pond as a marshy area. The mill building has now disappeared.
W J Crompton, RCAHMW, 9th May 2019.