Lieutenant-Colonel John By, R.E.
Born in London, England, about 1779, By graduated from the Royal Military Academy, Woolwich, in 1799. He was attached to the Royal Engineers in Canada (1802-1811) and later served in the Peninsular War. By was sent to Canada in 1826 to superintend the construction of an Ottawa River-Lake Ontario waterway from Bytown (Ottawa) to Kingston. The 198 km long Rideau Canal, built as a military route and incorporating 47 locks, 16 lakes, two rivers, and a 107 m long, 18 m high dam here at Jones Falls, was completed in 1832. On By's return to England charges, including the misappropriation of funds, were laid. Although entirely refuted, they essentially ended his career and he retired to his Sussex estate where he died in 1836.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.