...And that half of the country still does.

But...but he freed the slaves! (only in the states in rebellion)--Which had said he had no jurisdiction, and because Maryland wasn't in rebellion, technically, after the reconstituted legislature (after northern army occupation) failed to secede, the slaves there remained so until after the war.
I reckon they came in handy doing grunt work around the capital...
But he suspended the Writ of Habeas Corpus, and rounded up suspected Southern Sympathizers, who were sometimes paroled after they proved their innocence. Included in that group was Francis Scott Key's grandson, who was held prisoner in Fort McHenry for months.
The State Song begins: "The despot's heel is on thy shore! Maryland, my Maryland!"
The despot referred to by the writer (who was an expatriate Marylander during the war, and wrote the song in Louisiana) was none other than ol' 'Honest Abe', himself.
A later line: "Avenge the patriotic gore That flecked the streets of Baltimore."
...Refers to the Pratt Street Riots, which occurred when troops from the armies of Massachusetts and Pennsylvania invaded Maryland, at Lincoln's behest. The first KIA of the war were northern invaders, killed by crowds who pried up cobblestones to pelt them with (and members of the crowd protesting the invasion).
Of you believe the victor's fable, you get one impression, but if you dig, the earth is of a different color.