Raised in response to the Confederate cavalry raid into Maryland in mid-1864, the regiment guarded railroad bridges and garrisoned the Baltimore defenses during its month of service.

The 7th Delaware Infantry Regiment was organized at Wilmington, Delaware for 30 days emergency service on 12 July 1864, in response to Confederate cavalry commander Jubal Early's raid into Maryland and the Union defeat at the Battle of Monocacy, to guard the approaches to Wilmington.

[3] It was attached to the 3rd Separate Brigade of VIII Corps in the Middle Department, guarding the Philadelphia, Wilmington and Baltimore Railroad at Havre de Grace and Oconowingo Bridge until 16 July, when it moved to Baltimore and took positions in the defenses of that city.

Three men of the regiment died of disease before it returned to Wilmington on 11 August, where it mustered out at the end of its term on the next day.

[4][5] As it marched through the streets of Wilmington to Camp Smithers, the regiment was eagerly welcomed by the populace and the bell of the city hall was rung.