Melin Gwalchmai was probably built in the early 19th century, and was one of the last Anglesey mills to work by wind, ceasing circa 1927, after which it was worked by a diesel engine for some years. The sails were removed c1934 and the machinery removed in the 1940s. The tapered rubblestone tower is 8.75 metres high, and surrounded by a built-up mound in which there is a cellar 2.1 metres high and part-excavated into solid ground. When the cap was removed a flat concrete roof was fitted, and in 1975 the floors, stairs and major internal cross-timbers were in place. The drive machinery had been removed, but one bedstone remained in place, with some broken hangers below which had supported the tentering gear. Outside, the sack hoist spindle and a segment of a large wooden gear wheel, morticed for wooden teeth, were found. The later engine drive worked from a corrugated iron shed, a drive belt passing through a slot into the cellar.
By 2006 the floors, stairs and most of the major timbers had been removed, but the single bedstone was still in place and various pieces of Anglesey and french stones had been used to build up a wall adjacent to the tower.
W J Crompton, RCAHMW, 27 August 2008.