For the next four years, Gillmore was instructor of Practical Military Engineering at West Point and designed a new riding school.

[3] With the outbreak of the Civil War in early 1861, Gillmore was assigned to the staff of Brigadier General Thomas W. Sherman and accompanied him to Port Royal, South Carolina.

More than 5,000 artillery shells fell on Pulaski from a range of 1,700 yards during the short siege, which resulted in the fort's surrender after its walls were breached.

The result of the efforts to breach a fort of such strength and at such a distance confers high honor on the engineering skill and self-reliant capacity of General Gilmore.

Though long associated with engineering and artillery, Gillmore's first independent command came at the head of a cavalry expedition against Confederate General John Pegram.

Gillmore was assigned to replace Major General Ormsby M. Mitchel in charge of the X Corps after that officer's death from yellow fever.

Among the troops who assaulted Ft. Wagner was the 54th Massachusetts, a regiment of African-Americans led (as required by regulation) by white commissioned officers.

Gillmore had ordered that his forces be integrated and that African-Americans were not to be assigned menial tasks only, such as KP or latrine duty, but instead they were to carry arms into battle.

Gillmore decided on siege operations to capture Fort Wagner using innovative technology such as the 25-barreled Requa gun and calcium flood light to blind opponents during trenching efforts.

Federal reinforcements from the Gulf coast were being transferred East at the time and Gillmore was put in command of a detachment of the XIX Corps which had been quickly diverted to the defense of the capital at the battle of Fort Stevens.

With the threat to Washington over the XIX Corps was transferred to the Army of the Shenandoah and Gillmore was reassigned to the Western Theater as inspector of military fortifications.

Gillmore served on the city's Rapid Transit Commission that planned elevated trains and mass public transportation, and led efforts to improve the harbor and coastal defenses.

His son and grandson, both also named Quincy Gillmore, were West Point graduates, officers in the U.S. Army and generals in the New Jersey National Guard.

The traveling secretary of the Negro League's Kansas City Monarchs from 1920 to 1925 was named Quincy J. Jordan Gilmore.

It was a steam-powered tugboat "Hull #24" built for the Great Lakes Towing Company of Cleveland, Ohio, and launched around 1912–13.