1. In 1777, Maryland adopted a new state constitution on May 13. It was one of the first state constitutions to establish religious freedom and was an important precursor to the United States Constitution.

2. On May 13, 1861, Maryland Governor Thomas Hicks declared martial law in the state in an effort to prevent secession and keep Maryland part of the Union during the Civil War.

3. On May 13, 1913, the USS Maryland was launched from the shipyards in Newport News, Virginia. The battleship would go on to serve in both World War I and World War II.

4. The Maryland Jockey Club announced on May 13, 1939 that Pimlico Race Course would be the permanent home of the Preakness Stakes, one of the three major horse races that make up the Triple Crown.

5. May 13, 1988 marked the opening of Oriole Park at Camden Yards, the new home of the Baltimore Orioles baseball team. The ballpark is known for its retro design and was groundbreaking in its approach to stadium construction, ushering in an era of "retro-classic" ballparks.