This is Kirtland's Snkake (Clonophis kirtlandi). It is a really neat snake that is only found in small areas of the US in IN, IL, OH, and a few spots in nearby states. It is an endangered species over most of its range. You are lucky to have such a unique and rare critter in your yard. I hope you will protect them. Although....if you didn't know what it was, why were you handling it? This post was edited by FHFchrish on Fri, Sep 5, 14 at 9:25

That is a baby ratsnake (Pantherophis obsoletus). Completely harmless rodent eaters.

I assume that is a captive snake (or an escaped captive). While the pattern and coloration might first suggest that it is a striped morph California Kingsnake (Lampropeltis getula), the head shape and pattern tells a different story. The head shape looks to me like that of a milksnake (Lampropeltis triangulum). Therefore I am pretty sure this is one of the captive hybrids between a Cal King and a Milksnake.

The only poisonous snakes in Wisconsin will have a rattle at the end of their tails. Also, those are very very rare here. Also, snakes are your friends. They will keep rodent populations under control. They are generally very shy and won't bother you unless messed with, or stepped on (do not try to pick up).