Abraham Lincoln, who was desperate to prevent Maryland from joining the Confederacy (by force, if necessary), as such a turn of events would surround the Union capital of Washington, DC with hostile territory. The day after "Maryland, My Maryland" was first published, Lincoln suspended the writ of habeas corpus in Maryland. Subsequently, as Virginia's secession from the Union became imminent, Lincoln sent the Union Army to occupy Annapolis and Baltimore, and declared martial law. Over the course of the next few months, the Union arrested several thousand Marylanders suspected of Southern sympathies, including 30 members of the State legislature, a US Congressman representing Maryland, the mayor and police commissioner of Baltimore, and most of the Baltimore city council. These political detainees were imprisoned in Fort McHenry and Point Lookout without trial, in many cases, for several years.

These illegal and unconstitutional actions against Maryland cost Lincoln his life.

'Sic Semper Tyrannis'