I was wrong again. Well, half wrong. Here is a link to the old thread:

http://www.detroityes.com/mb/showthr...light=Savoyard

in looking at Silas Farmers 1891 book on Detroit, he sez the source of the Savoyard was near Riopelle and Congress, and headed west. There is an old map on the thread made by Farmer's dad in 1830 and modified/updated by Silas in 1890.