Fortifications

Fort C.F. Smith was a lunette that the Union Army constructed in Alexandria County (now Arlington County), Virginia, during 1863 as part of the Civil War defenses of Washington.  It was named in honor of General Charles Ferguson Smith, who died from a leg infection that was aggravated by dysentery on April 25, 1862. 

Fort C. F. Smith connected the Potomac River to the Arlington Line, a row of fortifications south of Washington, D.C., that was intended to protect the capital of the United States from an invasion by the Confederate States Army.

The Army built the lunette on a bluff overlooking the Potomac River and Spout Run. Because of its elevation and location, the lunette could protect the Aqueduct Bridge from invaders traveling along each of the two waterways. ( Source - Wikipedia )