The Great Rattlesnake Debate

My wife and I are having a discussion (you know... a disagreement or argument). She claims she saw a rattlesnake in Wisconsin. I say that this is proposterous. There aren't any rattlers this far North. They crave the heat, right?

It all started when sent me this message:

I'm interested in knowing what kind of snake this is that I saw in your parents driveway up North. It kinda looks like a type of rattlesnake, and according to the web, there are two kinds of venomous rattlers in Wisconsin (although there aren't many). Can you ask your listeners?

So I ask you, what kind of snake is this?

You guys aren't helping.