-- Last Updated: May-21-12 8:33 PM EST --
There are only two river systems in Michigan that border Canada. One is the St Clair/Detroit River that runs from Lake Huron to Lake Erie through Lake St Clair and Detroit. Unless your trip was over 100 years ago, there's not much wilderness on this route.
The second is the St Mary's River that runs from Lake Superior through Sault Ste Marie around Sugar Island and Drummond Island to Lake Huron. There are some areas of this river that are pretty remote, but this can also be big water.
Did you see any freighters during the trip? Both of these rivers have substantial freighter traffic.
Note that neither of these rivers would require any type of portaging.