1. The Winter Solstice - December 21 marks the winter solstice, the shortest day of the year and the official start of winter. In Illinois, this means the beginning of colder temperatures and potential snowfall.

2. The Birth of Jane Addams - In 1860, December 21 was the birthdate of social worker, suffragist, and Nobel Peace Prize winner, Jane Addams. Addams is famous for founding Hull House, a settlement house in Chicago that served to help immigrant communities in the city.

3. The Kaaba Stone Arrives - On December 21, 1945, the Kaaba Stone, an Islamic relic, arrived in Chicago, Illinois, after being gifted to the US government by King Ibn Saud of Saudi Arabia. The rock is considered sacred and is the focal point of the Hajj pilgrimage to Mecca.

4. Coal Mining Tragedy - On December 21, 1932, a coal mine in Moweaqua, Illinois, exploded, killing 54 miners. The disaster was one of several mining accidents in the region, highlighting the dangerous working conditions for coal miners in early 20th century Illinois.

5. Illinois Statehood - December 3, 1818, was the date that Illinois officially became the 21st state in the US. However, December 21 holds significance for Illinois as well, as it was the day when the first state government was inaugurated, with Shadrach Bond as the first governor.