The Trent Canal
In 1833 the Legislature of Upper Canada authorized improvements to the waterways of the Newcastle District, the first of which was a wooden lock here in Bobcaygeon. Three years later the first funds were appropriated for the opening of the waterway via the Trent River and the Kawartha Lakes to link Lake Ontario with Lake Simcoe (and later with Georgian Bay). This system was intended to open up the interior of the province, and to promote agriculture, lumbering and commerce.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.