How Ships Enter the Great Lakes: The St. Lawrence Seaway

Ships access the Great Lakes from the Atlantic via the St. Lawrence Seaway—a 370-km (230-mi) system of canals, locks, and channels bypassing Niagara Falls.

The Seven Locks (Upbound)

1. St. Lambert Lock (Canada)
2. Iroquois Lock (Canada)
3. Eisenhower Lock (USA)
4. Snell Lock (USA)
5. Upper Beauharnois Lock (Canada)
6. Lower Beauharnois Lock (Canada)
7. Côte Ste. Catherine Lock (Canada)

Operation

• Season: March 25 – Dec 31 (ice-free period); 24/7 during season.
• Control: Traffic Control Centre, Cornwall, ON — vessels check in for scheduling.
• Process: Ship enters lock → gates close → water level raised/lowered → gates open → proceed.
• Max Vessel (Seawaymax): 225.5 m (740 ft) LOA × 23.8 m (78 ft) beam × 8.08 m (26.5 ft) draft.

Economic Role

Moves ~40M tonnes/yr (iron ore, grain, coal, steel, project cargo). Connects Great Lakes ports (Duluth, Chicago, Detroit, Cleveland, Toronto) to global markets. Also a tourist attraction (lock viewing, boat tours).