The postmark on this cover commemorates the 200th anniversary of the war of 1812. On September 12, 1814, a decisive battle was fought against the British. The had landed a large invasion force at North Point with plans to take over nearby Baltimore. But they were met by American forces who delayed the attack on Baltimore, giving the Americans time to prepare for and successfully defend it.
Defenders Day is a holiday in the state of Maryland to commemorate the battle at North Point. Today, Fort Howard occupies the original battle site. They re-enact the battle every year and this year they did so on September 2.