In Sault ste Marie, stop by the Museum Ship Valley Camp. It's a converted ore carrier into Museum. It's got a lot of interesting things to do for kids, but also a lot of history about ore shipping on the lakes. It's also got a good memorial and information on the Edmund Fitzgerald. www.saulthistoricsites.com/ gives good information about the area also.
While you are in Duluth stop by the ore mines up in the Hibbing area (a good day drive). It also ties into the ore shipping and how iron ore is mined and the taconite pellets are made. You can go out and see the Hull–Rust–Mahoning operation and see the mining and pit area. Nice little park on the north side of Hibbing (it's actually part of the original town).
