There have been mills at Coultershaw from before the Domesday survey of 1086, until 1973 when the last mill was demolished. The mills were located here on the River Rother so that they could be powered by river water. Coultershaw had a variety of mills over the centuries- corn mills, fulling mills and malting mills.
At the time of the Domesday survey, carried out by King William the Conqueror 1086, a mill at Coultershaw was valued at an annual rent of 26 shillings and a bucket of eels. The Domesday survey recorded 5,624 water-powered corn mills in the country, one for every 300 inhabitants. Local farmers brought their grain to the mill to be ground into flour, with the miller receiving a proportion of the flour produced as payment for his work. Flour was produced by grinding grain between heavy horizontal stones powered by a waterwheel.
A variety of milling activities were carried out in the Coultershaw area, in number of mills rented by a number of different millers. In 1240 there may a have been a fulling mill here, which was used to prepare woollen cloth. By 1534, there were a malting mill and two corn mills on the site, and by 1666 there were three corn mills.
In 1907, John Gwillim, who already operated Fittleworth Mill and the North Mill at Midhurst, took a lease on Coultershaw Mill from the Petworth Estate. He modernised the mill replacing the grind stones and wooden machinery with steel shafting and rollers to grind the grain more efficiently. As John Gwillim operated the three watermills on the River Rother, he was able to control the flow of water to operate his mills in the most efficient way.
In 1923, the mill was destroyed by fire, and was rebuilt within 12 months, in steel and ferroconcrete. A garage was added to the east side, with a concrete and steel floor over the top of the Beam Pump.
John Gwillim died in 1929 and the business was continued by his son, Gordon. The mill was severely damaged by fire in 1946, but was repaired and continued in production. Gordon Gwillim died in 1970, and his widow Dorothy continued the business until it closed in October 1972 and the mill was demolished.