When was the last earthquake in Wisconsin?

I recommend the USGS earthquake site, which has a listing of the most recent earthquakes in (nearly) every state. At the time of this writing, it says the last earthquake in Ohio was October 24, 2010, near the Ohio/West Virginia border with the closest city being Marietta.

If you live in North Dakota or Wisconsin, there's no listing, as there have been no earthquakes of any significance (greater than 3.5 moment magnitude) there for at least 30 years.