The Wolseley Expedition 1870
In August, 1870, a force of British regulars and Canadian militia comprising some 1,200 men commanded by Colonel Garnet Wolseley, arrived in this area en route to the Red River to establish Canadian authority within the present province of Manitoba. The previous year the Hudson's Bay Company had agreed to transfer control of its western territories to Canada, and some local inhabitants, fearing loss of their lands and interference with their mode of existence, had set up a provisional government under Louis Riel to press their claims on the Dominion. The expedition had disembarked at Prince Arthur's Landing on Lake Superior and travelling by land and water reached Fort Garry on August 24.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.