One hundred and fifty years ago today and this weekend, Federal and Confederate troops skirmished on the outskirts of Washington, DC, three miles or so from where I sit. The Washington Post and other local news sources have items about the anniversary.
Federal forces under General David Hunter had been forced by lack of supplies to retreat from the Shenandoah Valley; their lack of ammunition meant that they had to retreat toward the Ohio River, rather than directly toward Harper's Ferry. This opened the valley to Confederate forces under Jubal Early, who crossed the Potomac, and moved on Washington. General Lew Wallace got together a scratch force of mostly raw troops, and fought a delaying action on the Monocacy River near Frederick. They Union force lost, but the Confederates were delayed a day, which gave Federal reinforcements, principally the 6th corps of the Army of the Potomac, to arrive from the James River.
July 12th and 13th saw skirmishing in front of Washington, mostly in the area around Fort Stevens, near present-day Piney Branch Road and Georgia Avenue, NW., though some Confederate cavalry made a reconnaissance in the direction of what is now the American University neighborhood. Fort DeRussy, in Rock Creek Park near Military Road, contributed fire support. Ultimately, Early decided that it was not worth trying to force his way into the city, and retreated.
Vestiges of the works and the battle remain. You can see the old earthworks at Fort Stevens from Piney Branch Road; you can see what is left of Fort DeRussy by walking a hundred yards or so in from the intersection of Military Road and Oregon Avenue, NW. Battleground National Cemetery, on Georgia Avenue, NW, between Van Buren St. and Whittier Place has graves of Federal soldiers; it occupies about a third of a city block. In the churchyard of Grace Episcopal Church in Silver Spring, about three miles north, there is a grave marker for some Confederate soldiers.
It certainly would have embarrassed the United States government to have the capital raided. Whether that would have had an effect on the war is less clear; there had been a year of successes by July 1864. Early's raid led to Philip Sheridan taking command of Federal forces in the Shenandoah Valley, where he defeated Early's forces at Fisher's Creek and Winchester, giving the US command of most of the valley.