1. On September 20, 1862, the 12th Wisconsin Volunteer Infantry Regiment fought in the Battle of Shepherdstown during the American Civil War. The regiment suffered heavy casualties, with over 200 soldiers killed, wounded, or missing.

2. The Green Bay Packers played their first NFL game of the 1931 season on September 20, defeating the Brooklyn Dodgers 7-0. This game marked the Packers' first of three consecutive NFL championships.

3. Wisconsin's first state fair was held on September 20, 1851, in Janesville. The three-day event featured exhibits and competitions showcasing the state's agricultural and industrial products.

4. On September 20, 1965, the University of Wisconsin-Madison welcomed its largest freshman class up to that point, with over 5,400 students enrolled. This influx of students marked a turning point for the university, as it grew into one of the largest and most respected public universities in the country.

5. The Milwaukee Brewers played their last game at Milwaukee County Stadium on September 20, 2000, against the Cincinnati Reds. The Brewers moved to their current home, Miller Park, the following season. The stadium, which also had served as the home of the NFL's Green Bay Packers, was demolished in 2001.