Rideau Canal (or Waterway), 202 km long, links the Ottawa River at Ottawa with Lake Ontario at Kingston. Conceived as the major component of an alternative route for military purposes between Montréal and Kingston, the Rideau Canal was first proposed as the War of 1812 drew to its close. Construction started (1826) according to the design, and under the direction, of Lieutenant-Colonel John By. About 50 dams were necessary to control the water levels at rapids on the Rideau and Cataraqui rivers. The 46 (originally 49) locks in use raise vessels 83 m from the Ottawa River to the portage channel at Newboro, whence vessels descend 50 m to Lake Ontario at Kingston.
The construction of the Rideau Canal - built in virgin forest with all work being done by hand - caused great hardship to its Irish labourers, many of whom died of malaria. Finished in 1832 after 5 summer working seasons, with up to 2000 men being employed by the Royal Engineers and appointed contractors, the canal ranks among the greatest early civil-engineering works of North America. Lieutenant-Colonel By located his headquarters at the junction of the Ottawa and Rideau rivers and started a small settlement, first named Bytown in his honour but renamed Ottawa in 1855.
Although it carried freight and passengers in small steamboats for a century, the Rideau Canal was never economically viable, and is now used entirely by pleasure craft. Most of the original locks and canal cuts are still in use, and, except for 3 hydraulic locks, all are still operated by the muscle power of lock staff cranking the distinctive "crab" winches. Its stone walls, ponds and bridges have preserved a quiet beauty along its course through the city of Ottawa, and in the wintertime it provides one of the world's most famous skating rinks. In 1926, 100 years after the beginning of the canal's construction, it was designated a national historic site. In 2000 it became part of the Canadian Heritage Rivers System. The Rideau Canal was designated as a United Nations World Heritage Site in 2007.