Construction of the Rideau Canal begins

Background. After the War of 1812, information was received about United States plans to invade the British colony of Upper Canada from upstate New York. To ensure safe passage for military vessels between Montreal and Kingston, a route was planned proceeding westward from Montreal, up the Ottawa River to the mouth of the Rideau River — later the site of Bytown — then southwest via short canals connecting natural water bodies to Kingston on Lake Ontario. Colonel John By was brought out of retirement in 1826 as Superintending Engineer for the project.

Engineering Preparation. Prior surveys by Sir Joshua Jebb in 1816 and Samuel Clowes in 1823-24 established the canal route. Clowes' survey discounted the Irish Creek Route due to an overland section. Lieutenant-Colonel John By, an experienced military engineer, was brought out of retirement in 1826 to supervise the construction, leveraging his prior engineering experience in Canada.

Site Selection. On 26 September 1826, Lieutenant-Colonel John By and the Earl of Dalhousie, Governor of British North America, chose the site as the beginning of the canal. The Royal Sappers and Miners under By used a sundial at the site, behind the present-day East Block on Parliament Hill and overlooking the set of locks, in 1826–27. By is credited with founding Bytown in the course of supervising the canal.