In 1817, Cass was one of the two commissioners (along with Duncan McArthur), who negotiated the Treaty of Fort Meigs, which was signed September 29 with several Native American tribes of the region, under which they ceded large amounts of territory to the United States [REF].
In 1820, Cass led an expedition to the northwestern part of the Michigan Territory, in the Great Lakes region in today's northern Minnesota.