1. Maryland was founded on December 21, 1632 by King Charles I of England, who granted a charter to George Calvert, the first Lord Baltimore. The charter established the colony of Maryland as a refuge for English Catholics, who were persecuted in England at the time.

2. On December 21, 1784, the Maryland General Assembly passed a law establishing the University of Maryland, the first public university in the United States. The university was founded in Baltimore and originally called the College of Medicine of Maryland.

3. On December 21, 1829, the first successful American steam-powered locomotive, the Tom Thumb, made its maiden voyage on the Baltimore & Ohio Railroad. The locomotive was designed by Peter Cooper and traveled 13 miles from Baltimore to Ellicott's Mills in just over an hour.

4. On December 21, 1916, the Jones Falls flood devastated parts of Baltimore, causing extensive damage and killing 10 people. The flood was caused by heavy rainfall and poor drainage systems in the city.

5. On December 21, 1972, Maryland Governor Marvin Mandel signed a bill legalizing parimutuel betting on horse races in the state. The bill allowed for the construction of several racetracks in the state, including Pimlico Race Course, home of the Preakness Stakes.