A 5 mile long sand bar separates Lake Superior from a natural harbor that transitions into the St. Louis River in Duluth, MN. At the beginning of last century an army of volunteers helped dig a canal that was spanned by this French-designed bridge. In it's original form a large basket was suspended and traveled along the top span to carry passengers from one side to the other. The current lower span was added later and is raised as needed to allow ship traffic into the harbor.