1. On December 21, 1865, the 13th Amendment to the United States Constitution was ratified in Missouri. This amendment abolished slavery and involuntary servitude, officially ending the practice in the state.

2. In 1937, a record-breaking snowstorm hit the state of Missouri on December 21. The storm brought over 20 inches of snow to some areas, causing widespread travel disruptions and power outages.

3. December 21, 2012, marked the end of the Mayan Long Count Calendar, which many people believed would bring about the end of the world. Despite these fears, the day passed without incident in Missouri and around the world.

4. On December 21, 1988, pan-Am Flight 103 was bombed over Lockerbie, Scotland, killing all 259 onboard and 11 people on the ground. The tragedy had a significant impact on the town of Columbia, Missouri, as a number of local residents and students at the University of Missouri were among the victims.

5. In 2004, the Missouri Supreme Court issued a ruling on December 21 that had far-reaching implications for public education in the state. The ruling established the Missouri School Improvement Program, a framework for evaluating and improving schools based on a set of measurable quality standards.