John Graves Simcoe had enormous impact on Canada and Mount Dennis. In September, 1793, Governor Simcoe travelled up the trail to Georgian Bay, and returned via what was to become Yonge Street. This decision led to the abandonment of the trail. He and his companions camped at 3rd line, which was to become Eglinton Avenue.
This was days after the passage of the Act Against Slavery , an anti-slavery law passed in the second legislative session of Upper Canada . Although not an outright abolition, t banned the importation of slaves and mandated that children born henceforth to female slaves would be freed upon reaching the age of 25. It is significant because it was the first British parliament to legislate an end to slavery, and had profound influence on the Underground Railroad, as it made Upper Canada a safe haven.
Simcoe mandated the construction of a sawmill on the west bank of the river near present-day Bloor Street which was operated by John Wilson. In 1797 Simcoe managed to get a grist mill established on the Humber River. It was owned and operated by John Lawrence. Over the years, numerous mills have been operated along the river by such men as William Cooper, W. P. Howland, Thomas Fisher, John Scarlett, William Gamble and Joseph Rowntree.