Saint Lawrence Seaway
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
An international waterway, about 3,781 km (2,350 mi) long, consisting of a system of canals, dams, and locks in the St. Lawrence River and connecting channels through the Great Lakes. Jointly developed by the United States and Canada, the seaway opened in 1959 and provides passage for oceangoing ships as far west as Lake Superior.