Why did the union want to keep MD in the union?
The US State of Maryland abbreviated by Md. was a slave state during the course of the US Civil War. It lay positioned north of Washington DC. If it joined the Confederacy, Washington DC would be virtually surrounded by slave states. There was strong pro-South sentiment in Maryland. The important port of Baltimore, Md. would also be valuable to the South. Thus, Lincoln used armed force and curtailment of certain civil liberties to keep Maryland in the Union.