Niagara Portage Road
Following the cession of the east bank of the Niagara River to the United States in 1783, the British authorities felt compelled to transfer the portage road around Niagara Falls to the west bank of the river. Opened in 1789 by a group of private traders led by Robert Hamilton, the road between Queenston and Chippawa, which passed to the east of this monument, became the official government route in 1791. Until the completion of the Welland Canal in 1829 and the building of railways in the 1850's, it was the principal link in trade, travel, and war between Lake Ontario and the upper lakes.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.