A freight ship, the CSL St. Laurent, passes through the Iroquois Lock of the Saint Lawrence Seaway at the United States-Canada border. The ship is only a few centimeters narrower than the lock. The Saint Lawrence Seaway is a system of locks, canals and channels in Canada and the United States that permit ocean-going vessels to travel from the Atlantic Ocean to the Great Lakes, as far inland as the western end of Lake Superior.