1. On May 20, 1856, the city of Ripon, Wisconsin was founded. Ripon is known for being the birthplace of the Republican Party, as a meeting held there in 1854 led to the creation of the party.

2. On May 20, 1919, Milwaukee County Stadium opened. The stadium was home to the Milwaukee Braves and later the Milwaukee Brewers until it was demolished in 2001.

3. May 20, 1932 was the day that Amelia Earhart flew solo across the Atlantic Ocean, making her the first woman to accomplish this feat. Although she did not land in Wisconsin, the state welcomed her with a celebration when she arrived in New York City.

4. On May 20, 1964, the Milwaukee Braves played their last game at County Stadium before moving to Atlanta. The team had been in Milwaukee for 13 seasons.

5. May 20, 1970 was the day that the University of Wisconsin-Madison protest against the Vietnam War ended in violence. National Guard troops were sent in to disperse the protestors, resulting in injuries and arrests. The event is known as the "May 1970 events" and was a significant moment in the anti-war movement.