Lieutenant-Colonel John By, R.E., 1779-1836
Born in Lambeth, London, By graduated from the Royal Military Academy, Woolwich, in 1799. With the Royal Engineers in Canada (1802-1811) he was engaged in the reconstruction of the fortifications at Quebec and later served in the Peninsular War. In 1826 By was again sent to Canada to superintend construction of an Ottawa River-Lake Ontario waterway. Its eastern terminus was "Bytown", later named Ottawa. The resulting Rideau Canal, an outstanding engineering feat designed primarily for military purposes, was completed in 1832. However, on his return to England, he was charged with spending funds not authorized by the British parliament. Although entirely refuted, this accusation essentially ended his military career and he retired to his Sussex estate, where he died.
Plaque via Alan L. Brown's site Ontario Plaques. Full page here.