The area had been previously shaken by the 1909 Wabash River earthquake, causing damage assessed at VII (Very strong) on the Modified Mercalli scale across the Wisconsin-Illinois border.
Shocks in 1919 and 1925, the first from Missouri and the latter from Canada, occurred over enormous zones and affected the entire region, though not seriously.
[2] The area hardest hit was a 7,770 square kilometers (3,000 sq mi) strip of land in southeastern Wisconsin, while the earthquake was felt over a much more extensive 99 miles (159 km) wide area stretching across the Wisconsin-Illinois border, and to Lake Michigan and Waukesha.
[4] Numerous calls were made local fire departments, police stations and newspapers.
[4] Often described as "sharp", this was the most powerful earthquake to date in Wisconsin's seismological history.