1. On December 20, 1777, the Battle of Matson's Ford occurred during the American Revolutionary War. The Continental Army, under the command of General George Washington, successfully crossed the Schuylkill River near Valley Forge and defeated a British regiment stationed at Matson's Ford.

2. In 1860, Maryland's Governor Thomas H. Hicks called for a special session of the state legislature to discuss the crisis of secession and the upcoming Civil War. Despite strong pressure from pro-Confederate factions, Maryland ultimately remained in the Union.

3. December 20, 1934, marked the opening of the first high-security federal prison in the United States, located on Alcatraz Island in San Francisco Bay. Originally built as a military prison in the late 19th century, Alcatraz became notorious as a maximum-security facility for dangerous criminals such as Al Capone and Robert Stroud.

4. On this day in 1951, pitcher Jim Palmer was born in New York City. Palmer went on to become a star player for the Baltimore Orioles, winning three Cy Young Awards and helping the team win three World Series titles.

5. In 2014, the Maryland Court of Appeals upheld a decision granting same-sex couples the right to marry in the state. The ruling marked a major victory for LGBTQ rights advocates in Maryland and across the country.