unloaders. -- the cargo would be removed, primarily if it was iron ore, with hewlett iron ore unloaders. they were mechanized arms that were attached to massive dockside infrastructure which would reach down through the cargo holds of the vessel. with these huge clamshell buckets, they would scoop up to tons to three tons of cargo each time. take them out of the cargo hold and deposit them in railroad cars waiting at dockside. a boat like this could take 7-10 hours to unload, which was a vast improvement over earlier systems of unloading which could take a day and a half, two days sometimes. boats on the great lakes are always looking for as many cargoes as they can possibly carry. they generally have a principal cargo. for many years, all freighters tried to carry iron ore, which was the main cargo. but there is also coal, which is still shipped on the great lakes. stone aggregate used in the creation of steel. limestone. construction material stone. today, salt is mined in the great lakes region and carried by boat from city to city for road salt. they carry a variety of products. ther