1. On January 20, 1820, Missouri was officially admitted as the 24th state of the United States. This followed a long debate over whether Missouri would be a free or slave state, which was eventually resolved through the Missouri Compromise.

2. January 20, 1862 saw the Battle of Fredericktown take place in Madison County, Missouri. This was a small but significant engagement in the Civil War, with Union troops successfully repelling a Confederate force and securing the area for the Union.

3. In 1937, on January 20, the University of Missouri's School of Journalism was the first in the world to offer a master's degree in journalism. This was a groundbreaking development in the field of journalism education and helped to establish Missouri as a leader in the industry.

4. On January 20, 1985, a record-breaking cold snap hit Missouri and much of the central United States. Temperatures plummeted to below zero degrees Fahrenheit, leading to widespread power outages, transportation disruptions, and other problems.

5. More recently, January 20, 2017 saw significant protests and rallies take place across Missouri and the United States as Donald Trump was inaugurated as the 45th President of the United States. Demonstrators marched in St. Louis, Kansas City, Springfield, and other cities, expressing concerns over Trump's policies on immigration, healthcare, and other issues.