The 13th Maryland Infantry was organized on November 15, 1861 for 3 years service. It was organized in Westminster, MD and was composed of men from Sykesville, MD. The commanding officer was Colonel James Francis.

The unit was sent to the defenses of Baltimore for 2 months, and was placed in Louis Blenker's division in the Army of Virginia

Army of Virginia

The Army of Virginia was organized as a major unit of the Union Army and operated briefly and unsuccessfully in 1862 in the American Civil War. It should not be confused with its principal opponent, the Confederate Army of Northern Virginia, commanded by Robert E...

. The regiment fought at Cedar Mountain

Cedar Mountain

Cedar Mountain, also known as Slaughter Mountain, is a piedmont monadnock in Culpeper County, Virginia. The ridge is south of the town of Culpeper and just to the northwest of the northern tip of the Southwest Mountains at Clark Mountain. The mountain was the site of the Battle of Cedar...

 and 2nd Manassas, and was praised by General Nathaniel Banks as "one of the most effective regiments under fire I have commanded." The regiment was later detached for garrison duty in Frederick, MD on September 3. During the Antietam Campaign, the regiment was forced to retreat from Frederick with other Maryland militia units due to the advance of forces under Stonewall Jackson

Stonewall Jackson

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. It was transferred as a replacement for regiments in the Vermont Brigade that was decimated at Antietam to IX Corps, Army of the Potomac. At the battle of Fredericksburg, the regiment was held in reserve. On January 2, 1863 the regiment was sent west to Kentucky for operations against Confederate irregular partisans. The regiment was sent detached as part of the garrison of Nashville, where it stayed for 9 months. The regiment was then sent to be
part of II Corps, Army of the Potomac under the command of General Caldwell. The regiment was attacked by the 4th Alabama Regiment during the battle of Spotsylvania Courthouse and was cited for gallantry when it beat back the attack, and counterattacked into the woods on the left flank of the Union line and drove back the rebels. The regiment participated in the Siege of Petersburg and was mustered out of service in November. The regiment lost 1 officer and 13 men to disease, and lost 3 officers and 76 men in battle.