Maryland put "War of 1812" on the plates because of the Battle of Baltimore, specifically the siege of Fort McHenry, which inspired Marylander Francis Scott Key

Maryland put "War of 1812" on the plates because of the Battle of Baltimore, specifically the siege of Fort McHenry, which inspired Marylander Francis Scott Key to write the poem that would later become the national anthem. Fort McHenry is in the lower left of the license plate. The star spangled banner flies above it. The "bombs bursting in air" are the fireworks. It doesn't commemorate the war, it commemorates the anthem, it just says "War of 1812" because that's when the event occurred. It was a terrible design but I've got amateur radio plates so I avoided it.