1. June 21, 1788: Maryland ratifies the United States Constitution, becoming the seventh state to do so. Maryland played a pivotal role in the formation of the country, with its capital, Annapolis, serving as the site for the Constitutional Convention in 1786.

2. June 21, 1864: The Battle of Jerusalem Plank Road takes place during the American Civil War. Union forces led by Generals Winfield S. Hancock and David Birney engage Confederate troops under General Robert E. Lee. The battle is part of the Siege of Petersburg and lasts two days, resulting in over 900 Union and Confederate casualties.

3. June 21, 1941: Bethany Beach becomes the first official beach to integrate in the United States. The beach had been a popular spot for African-American vacationers, but they were often relegated to separate areas. This changed when the town council passed an ordinance allowing for the integration of the beach.

4. June 21, 1990: Maryland Governor William Donald Schaefer declares a state of emergency in response to a severe heat wave. Temperatures in some parts of the state exceed 100 degrees Fahrenheit, and several people die from heat-related causes. The state government opens cooling centers and distributes bottled water to those in need.

5. June 21, 2006: The United States Supreme Court rules that the death penalty cannot be imposed on individuals who were under the age of 18 when they committed their crimes. The decision, in the case of Roper v. Simmons, strikes down the laws of 20 states, including Maryland, that had allowed for the execution of juveniles.