Short answers, pulled from the story.
The 1860 Federal Census showed nearly as many free blacks (83,942) as slaves (87,189). This demographic reality created deep internal divisions across the region. Southern and Eastern Shore counties prospered on tobacco trade and slave labor while Central and western regions had stronger economic ties to the North.
The first bloodshed of the Civil War occurred in Maryland on the 19th of April 1861. A mob of Marylanders attacked soldiers from Massachusetts who were marching through Baltimore. Four soldiers and twelve civilians died in the riot.
About 4,000 Marylanders traveled south to fight for the Confederacy despite their home state remaining in the Union. Official records credit Maryland with 33,995 white enlistments in volunteer regiments plus 8,718 African American enlistments in United States Colored Troops. Estimates vary widely about total Confederate enlistments from Maryland ranging between 3,500 and just under 4,700 men.
The Battle of Antietam occurred the 17th of September 1862 near Sharpsburg, Maryland. It became the single bloodiest day in American military history with Union forces suffering 12,401 casualties including 2,108 dead. President Lincoln used this strategic victory to issue the Emancipation Proclamation effective the 1st of January 1863.
Thousands of Confederate soldiers were held at Point Lookout prison camp located in St. Mary's County near Chesapeake Bay between 1863 and 1865. Of approximately 50,000 Southern soldiers detained there nearly 4,000 died representing an eight percent death rate among those imprisoned. Camp Parole in Annapolis served as another holding area where around 70,000 soldiers passed through until Ulysses S Grant assumed command in 1864.
A constitutional convention met at Annapolis in April 1864 to rewrite Maryland's fundamental law and Article 24 outlawed slavery within state borders. Voters approved the measure narrowly on the 13th of October 1864 by margins of 30,174 to 29,799. The constitution took effect the 1st of November 1864 making Maryland the first Union slave state to abolish slavery during the war.