"Dundas Mills"
By 1799 the Morden family had a sawmill near this site on Spencer Creek north of Dundas Street. They sold this property in 1800 to Edward Peer who built a grist-mill about 275 metres southeast, close to Dundas Street, and adopted the name "Dundas Mills". Peer sold the property in 1804 to Richard and Samuel Hatt and a partner, but by 1807 Richard had become sole owner. Then or slightly earlier, Richard Hatt built northwest of Peer's grist-mill the tall stone flour mill which stood near this site until 1968. The other mills were destroyed long before. The community of "Dundas Mills" became part of the town of Dundas in 1847.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.