Few people know about the extensive Defenses of Washington. By the end of the US Civil War, Washington DC was the most fortified and protected city in the world. Nearly 70 forts and 90 artillery batteries surrounded the perimeter of the US Capital. For if one would consider that it was an island among those who had rebelled with the states of Virginia seceding and Maryland remaining a slave state. These Defenses of Washington are noted by a Commonwealth of Virginia historical marker and complemented by other historical markers erected by the Commonwealth and the US National Park Service and localities. On the southern side, Arlington House was used as the headquarters. It would be here that General Amiel Weeks Whipple and President Abraham Lincoln would often meet to have lunch and the President get the briefing while wrapping his arms around Whipple's two sons.
When the war first began in earnest with the bombardment and siege of Fort Sumter in Charleston, South Carolina harbor, Major Robert Anderson surrendered the fort to the Confederates. Back in Washington DC, the Union Army soon went across the Potomac River and occupied the high ground of Arlington Heights (also known as part of the Custis-Lee estate) and quickly built fortifications at both Long Bridge (Fort Runyon) and Aqueduct Bridge (Fort Corcoran) to stop any invasion across those river crossings. It was thought then to be sufficient protection, until the Battle of Bull Run.
Fort Cass, a lunette, had been built on Arlington Heights as a defense from an attack from the west. After the Union Loss at the First Battle of Bull Run, the US Army leadership convened and decided to augment the perimeter defenses. General George B McClellan would designate where and General John Gross Barnard would design and oversee the construction of the fort.
It would be 1863 before the fort that would ultimately become Fort Myer would be built. Fort Whipple was built on the most Northeastern part of Arlington Heights overlooking Washington DC. Designed by General Barnard, it was considered an outstanding design for a fort. Placement was determined where General Amiel Weeks Whipple had ordered an observation balloon aloft to recon what the Confederates were doing to the west.
An excellent map of the Defenses of Washington has been produced by the US National Park Service showing the sites and which locations are managed by the NPS.
Additional reading about the Defenses of Washington and the battle of Fort Stevens is presented by The Civil War Trust
During the Civil War the City of Alexandria Virginia was a center of activity for the Union. Since then the city has done a fine job to preserve and present its Civil War heritage with the restoration and preservation of Fort Ward with a museum and the more recent effort to construct the Civil War Bike Trail with the cooperation of Arlington and Fairfax Counties in Virginia.
Images of America - Fort Myer tells the story of the one and only remaining active fort from the Defenses of Washington. Over 200 historical photographs are included in the book.
Another book which details all the defenses - the forts and batteries with maps, photos from private collections is the revised version of Mr Lincoln's Forts that is written by Benjamin Franklin Cooling and Walton Owens. Another interesting read is the book just published in November 2011 is Civil War Northern Virginia 1861 (The History Press) (Civil War Sesquicentennial) written by William S. Connery.