| @MisterF, the borders in the Great Lakes are not "arbitrary". They are codified in law. From the Twenty-Fourth Congress, when Michigan was admitted to the United States:
:...the said State (Michigan) shall consist of and have jurisdiction over all of the terrority included within the following boundaries, and over none other, to wit: ...thence, with the said boundary line between the United States and Canada thorugh the Detroit River, Lake Huron, and Lake Superior, to a point where the said line last touches Lake Superior; thence, in a direct line through Lake Superior, to the mouth of the Montreal river..."
You can see this boundary line on practically any online map (Google maps, Bing maps, etc.).
http://img703.imageshack.us/img703/6152/bordeso.jpg |