The Middle Department was an administrative military district created by the United States War Department early in the American Civil War to administer the troops in the Middle Atlantic states. The department was created on March 22, 1862 by the Adjutant General's Office in Washington, D.C. It combined all Federal troops in the states of New Jersey, Delaware, Pennsylvania and the counties of Anne Arundel, Baltimore, Cecil, and Harford in Maryland, with headquarters in Baltimore, Maryland. Maj. Gen. John A. Dix was designated as its first commander.