It has been generally accepted that Michigan was nicknamed "The Wolverine State" for the abundance of wolverines that once roamed the peninsula. However, according to the Michigan Historical Center, wolverines were very rare in Michigan if they were present at all. It's not clear how this nickname originated, but there are two theories.
Some think the nickname was originated by Ohioans in 1835 during a dispute over an Ohio/Michigan boundary called the "Toledo Strip." This dispute became known as the
Toledo War. Though Michigan and Ohio both sent troops to the area, no shots were ever fired. It's said that Ohioans, at that time, referred to Michiganians as "...as vicious and bloodthirsty as wolverines."
Another theory is proposed that Native Americans compared the way that settlers were taking land, in the 1830s, to the way the excessively greedy wolverine went after its food.