It's inside the District of Columbia, actually. Fort DeRussy was only one of a ring of small earthenworks forts that surrounded Washington, D.C. during the Civil War.
When Jubal Early attacked Washington, D.C. in 1864, his attack fell on Fort Stevens whose left was guarded by Fort DeRussy.
Today, Fort DeRussy's formerly open fields of fire are completely reclaimed by woodland and trees grow out of it's earthen parapets.
