1. On December 21, 1826, Michigan's first state constitution was ratified, paving the way for Michigan's eventual admission into the Union in 1837. The constitution established the state's government structure and enshrined certain rights for citizens.

2. In 1913, the Michigan State Capitol Building was dedicated on December 21. The building, located in Lansing, was designed by architect Elijah E. Myers and features a dome that is 267 feet tall.

3. December 21, 1937, saw the first flight of the Vultee XP-54, an experimental fighter aircraft developed by the Vultee Aircraft company in Detroit. The XP-54 was a unique design with two engines mounted behind the pilot and a complex set of controls, but it ultimately did not enter production due to its high cost and technical challenges.

4. On December 21, 1955, a major snowstorm struck southern Michigan, dumping over a foot of snow in some areas and causing widespread travel disruptions. The storm led to a state of emergency being declared, with the National Guard called in to help clear roads and assist stranded motorists.

5. December 21, 1971, saw the first broadcast of Michigan Radio, a public radio station based at the University of Michigan in Ann Arbor. The station now reaches over 500,000 listeners every week and produces a range of news, talk, and cultural programming.