Fort DeRussy was built on a high hill with the purpose of providing cross fire upon the approaches to Fort Stevens on the 7th Street Pike (now Georgia Avenue) and, together with Fort Kearney and Fort Reno to the west, controlling the country roads between Rockville Pike and Rock Creek Valley. It was built in 1861 by the 4th New York Heavy Artillery and named after Union Brig. Gen. Rene Edward Derussy, Superintendent of the United States Military Academy (1833 – 1838). The commander of the 4th New York Heavy Artillery was Colonel (later promoted to General) Gustavus A. DeRussy, Rene DeRussy’s son.
Between Fort DeRussy and Fort Kearney were located auxiliary batteries which added their fire to that of the fort, sweeping the slopes of minor depressions and commanding portions of the valley otherwise unseen. These works were supported by rifle trenches which were almost continuous from Fort Reno to Fort Kearney and thence, interrupted by the valley of Broad Branch, to Fort DeRussy.
On July 11 and 12, 1864, when a Confederate force under General Jubal A. Early attacked Fort Stevens to the east of the fort, Fort DeRussy became heavily engaged in supporting action. Altogether, Fort DeRussy had 11 guns and mortars which fired a total of 109 rounds to aid in the defense of Fort Stevens. Its 100-pounder Parrot rifle was the largest piece of artillery in the engagement and was very effective in checking the Confederates' advance. It had a range that reached nearly all the way to Silver Spring, Maryland, and could destroy large bodies of troops.
Fort DeRussy is in a good state of preservation . The parapet, which consists of high earth mounds with openings where guns were mounted, and the deep ditch (dry moat) around the parapet, remain in clear and distinct outline. Also, there is visible evidence of where the powder magazines were located inside the fort. On the outside, near the fort, well-defined rifle trenches extend in each direction.