"A Busy Day in the Canal," Tugboat Towing a Lumber Schooner, Charlevoix, Michigan, 1900

Large vessels were easy to maneuver on the open water, but much harder to control in tight spaces -- a particular problem in narrow Great Lakes harbors. Tugboats moved larger watercraft through these confines and positioned them into constricted docks. Bow thrusters -- additional propellers built into a large vessel's forward end -- have eliminated much need for tugboats on the Great Lakes.