In 1832 or earlier William Dewstow built a grist mill on the south side of Spencer Creek at the foot of Main Street, calling it the Wentworth Grist Mill. In 1833 Robert Holt, newly arrived from England, purchased the mill but Dewstow continued to operate it until 1850. The mill burned down in 1863, together with an adjacent brewery that Holt built in partnership with Henry Gray, also newly arrived from England.
John Wilson purchased the ruins in 1863 and built a larger grist mill with five run of stones, making it the largest such mill in Dundas. It was equipped to make oatmeal and cornmeal as well as flour and grist. In its heyday the mill could turn out 600 barrels of flour, 450 barrels of oatmeal, 200 barrels of cornmeal and 500 bags of grist per week. The mill employed eight men. Initially, a 50 horsepower waterwheel provided the power. Holt had constructed a dam just upstream of the Main St. bridge, and two millraces directed the flow to mills on both sides of the creek, including his own on the south side.
Later, a 50 horsepower steam engine was installed when the flow in Spencer Creek was substantially reduced in summer because of deforestation in the watershed. The mill burned down again in 1892, but the ruins were resurrected for a short time when the Bibby Brothers built a willow basket factory which operated from 1902 to 1904.