Newmills Corn and Flax Mills are situated west of Letterkenny in the small town of Milltown in County Donegal, Ireland. It features one of the largest, still working, waterwheels in the country.  The millrace is 1 km long and powers two separate millheels, one for grinding oats and barley and the other for flax.
The Corn and flax mills have been located there since the early 1800s when the Joseph Hunter. This combination of corn and flax mills is found mainly in Ulster where both types of mill were intimately linked to the surrounding farming economy. In 1861, Joseph Hunter sold the mills to John Devine and when Patrick Gallagher moved to Newmills in 1892, he bought the complex from William Devine, John's son. In addition to the mills, Gallagher purchased a residence, public house, grocery and ancillary buildings, including a scutcher's cottage This was located in a field beside the mill pond. The complex also included a forge on the opposite side of the road as well as a sizable farm of land. The business at Newmills was continued by his son, P.F. Gallagher until his death in 1980.
In 1892 the buildings were in a very poor state of repair and, according to the Valuation Office, the corn mills were disused and had been converted to use as farm buildings. Patrick Gallagher made extensive improvements to the corn mill around 1907 when he fitted the waterwheel present today as well as improving the machinery within the mill. During the Second World War, P.F. Gallagher took advantage of the revival of the flax industry when the British Government offered grants to increase the production of flax to guarantee the supply of linen for the war effort. He demolished a small single-storey flax mill in the early 1940s to make way for the relatively modern looking building. The public house and grocery were an important part of the whole enterprise and proved quite successful in the early years of the 20th century. Indeed, a lively export trade developed and when Sir Thomas Lipton started his grocery business in Glasgow, he received his first consignment of butter, bacon, eggs from Newmills.
The importance of Newmills was recognised in a 1978 An Foras Forbatha inventory of industrial archaeological monuments which identified it as by far the best example of a mill complex in County Donegal. In 1986, the mills were purchased by the state for preservation as a national monument.