The St. Lawrence Seaway opened to navigation in 1959. Construction of the 189-mile (306-kilometer) stretch of the Seaway between Montreal and Lake Ontario is recognized as one of the most challenging engineering feats in history. Seven locks were built in the Montreal-Lake Ontario section of the Seaway, five Canadian and two U.S., in order to lift vessels to 246 feet (75 meters) above sea level.
The 28-mile (44 kilometer) Welland Canal is the fourth version of a waterway link between Lake Ontario and Lake Erie, first built in 1829. The present canal was competed in 1932, deepened in the 1950s as part of the Seaway project, and further straightened in 1973. Today its eight locks, all Canadian, lift ships 326 feet (100 meters) over the Niagara Escarpment.