The Bruce Mines
The original claim to the Bruce Mine location was filed in September, 1846 by James Cuthbertson. It was acquired the following year by the Montreal Mining Company, and production commenced in 1847-48 at what became the first commercially successful copper mine in Canada. Employing skilled Cornish workers, the company operated the mine until 1865 when it was purchased by the West Canada Mining Company. That firm had leased part of the property in 1853 and opened the nearby Wellington and Copper Bay Mines. Though the Bruce Mines were among the more productive on the continent, declining profits forced them to close in 1876, and subsequent attempts to resume operations met with limited success.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.