1. On June 20, 1632, King Charles I of England granted a charter to Cecil Calvert, 2nd Baron Baltimore, for the territory of Maryland. This charter established the Province of Maryland as a proprietary colony, which would be governed by members of the Calvert family for over 50 years.

2. In 1756, during the French and Indian War, Maryland Governor Horatio Sharpe declared a state of emergency and called for the formation of two companies of rangers to defend the frontier against French and Native American attacks. These rangers were instrumental in protecting western Maryland during the war.

3. On June 20, 1863, during the Civil War, Union troops under General George Meade arrived in Frederick, Maryland. Meade would go on to command the Army of the Potomac at the pivotal Battle of Gettysburg, which began just a few days later on July 1.

4. In 1933, the Maryland State Athletic Commission was established. This commission oversaw all professional boxing and wrestling events in the state, and also had the power to sanction other sports such as mixed martial arts and kickboxing.

5. On June 20, 2008, the Baltimore Orioles defeated the Houston Astros 3-2 in 13 innings, in the first ever interleague game played at Oriole Park at Camden Yards. The Orioles later became the first team in American League history to win 11 straight extra innings games in a single season.