1. On December 21, 1843, the Milwaukee and Mississippi Railroad, now known as the Chicago, Milwaukee, St. Paul and Pacific Railroad, was incorporated in Wisconsin. This railroad played an instrumental role in the development of Wisconsin's infrastructure and economy.

2. In 1863, on December 21, Wisconsin's Civil War Governor, Edward Salomon, issued a proclamation calling for volunteers to fill the state's quota for troops. Wisconsin was one of the most important Union states during the Civil War, sending more than 90,000 soldiers to fight in the conflict.

3. December 21, 1917, marked the coldest day in Wisconsin's recorded history. The temperature fell to minus 55 degrees Fahrenheit in the small town of Couderay, located in northern Wisconsin. This extreme cold caused many hardships and challenges for Wisconsin residents at the time.

4. On December 21, 1932, the Wisconsin State Capitol Building in Madison was dedicated. This iconic structure, designed by architect George Post, stands as a testament to Wisconsin's cultural and political heritage.

5. In 1970, on December 21, the Milwaukee Bucks played their first game at the then-new Milwaukee Arena, now called the UW-Milwaukee Panther Arena. This marked the beginning of a new era in Milwaukee sports, as the Bucks would go on to win a championship just two years later in 1971.