in the St Marys River The waterway allows passage from the Atlantic Ocean to the inland port of
Duluth on Lake Superior, a distance of and to
Chicago, on Lake Michigan, at . The elevation change from Lake Superior to sea level is . Together with the
Saint Lawrence Seaway, the Waterway accommodates both ocean-going vessels and ore, grain, and coal-bearing
lake freighters that travel from
the system's saltwater outlet to its
far interior. The Waterway has larger
locks and deeper
drafts than the lower Seaway, limiting large freighters to the four lakes upstream of the Welland Canal and Lake Ontario and similarly restricting passage beyond
Saint Lambert, Quebec by larger ocean vessels. The two waterways are often jointly and simply referred to as the "St. Lawrence Seaway", since the Great Lakes, together with the
St. Lawrence River, comprise a single navigable body of
freshwater linking the
Atlantic Ocean to the continental interior. Major ports on the Great Lakes Waterway include
Duluth-Superior, Chicago, Detroit,
Toledo, Cleveland,
Two Harbors,
Hamilton and
Thunder Bay. Shipping channels separate upbound traffic from downbound traffic. The upbound direction is away from the St. Lawrence River (westerly or northerly except in Lake Michigan where upbound is southerly). Channels are marked with navigation buoys in constricted areas and pilots are required on foreign boats. Recreational boats can use or cross the ship channels, but the large boats, with limited maneuverability, have right of way. ==Map==