How many earthquakes happened in Wisconsin?

Wisconsin is not located near a plate boundary so there is very limited tectonic activity.

According to the US Geological Survey the last earthquake recorded in Wisconsin of note was a magnitude 4.2 event that occurred on 6 May, 1947 causing very minor damage (some broken Windows) in the City of Kenosha. People in other areas (the Earthquake was felt over a 7770 square kilometer area of southeastern Wisconsin) reported that the shaking caused plates or glasses to fall from shelves, however no people were injured during the event!

The majority of other earthquakes felt by people in Wisconsin actually occurred in other states or in Canada.

This is backed up by the seismic hazard map for Wisconsin which shows that earthquakes likely to occur in Wisconsin will typically have very low ground accelerations.