A whaleback was a type of cargo steamship with a hull that continuously curved above the waterline from vertical to horizontal. When fully loaded, only the rounded portion of the hull (the “whaleback” proper) could be seen above the waterline. With sides curved in towards the ends, it had a spoon bow and a very convex upper deck. It was formerly used on the Great Lakes of Canada and the United States, notably for carrying grain or ore.
The term developed in common usage in response to the ship’s appearance when fully loaded. A total of 44 such vessels were constructed from 1887 to 1898.