Maryland was a slave state. (As was Delaware.) The Emancipation Proclamation only affected slavery in states still in rebellion as of January 1, 1863, of which Maryland was not one.
I think Delaware had like 100 or 200 slaves.
I am aware of maryland and read the book about the plot to kill lincoln at the baltimore train station when he switched trains to go south for his first inauguration.
Didn’t Lincoln send troops to Baltimore to ensure troop trains from NY and NE got to the battlefields?