The Welland Canal is a ship canal in Ontario, Canada, connecting Lake Ontario and Lake Erie. It forms a key section of the St. Lawrence Seaway. Traversing the Niagara Peninsula from Port Weller to Port Colborne, it enables ships to ascend and descend the Niagara Escarpment and bypass Niagara Falls.
Approximately 40,000,000 tonnes of cargo are carried through the canal annually by about 3,000 ocean and Great Lakes vessels. It was a major factor in the growth of the city of Toronto. The original canal and its successors allowed goods from Great Lakes ports such as Cleveland, Detroit, and Chicago, as well as heavily industrialized areas of the United States and Ontario, to be shipped to the port of Montreal or to Quebec City, where they were usually reloaded onto ocean-going vessels for international shipping.
The Welland Canal eclipsed other, narrower canals in the region, such as the Trent-Severn Waterway and, significantly, the Erie Canal by providing a shorter, more direct connection to Lake Erie.
The southern, Lake Erie terminus of the canal is 99.5m higher than the northern terminus on Lake Ontario. The canal includes eight 24.4m ship locks. Seven of the locks (Locks 1–7, the 'Lift' locks) are 233.5m long and raise (or lower) passing ships by between 43 and 49ft each. The southernmost lock, (Lock 8 – the 'Guard' or 'Control' lock) is 349.9m in length. The Garden City Skyway passes over the canal, restricting the maximum height of the masts of the ships allowed on this canal to 35.5m.
All other highway or railroad crossings of the Welland Canal are either movable bridges (of the vertical lift or bascule bridge types) or subterranean tunnels. The maximum permissible length of a ship in this canal is 225.5m. It takes ships an average of about eleven hours to traverse the entire length of the Welland Canal.